Palladium-Catalysed Coupling Reactions

NARCIS (Netherlands)

de Vries, Johannes G.; Beller, M; Blaser, HU

2012-01-01

Palladium-catalysed coupling reactions have gained importance as a tool for the production of pharmaceutical intermediates and to a lesser extent also for the production of agrochemicals, flavours and fragrances, and monomers for polymers. In this review only these cases are discussed where it seems

Overexpression of the cytosolic cytokinin oxidase/dehydrogenase (CKX7) from Arabidopsis causes specific changes in root growth and xylem differentiation

Czech Academy of Sciences Publication Activity Database

Kollmer, I.; Novák, Ondřej; Strnad, Miroslav; Schmülling, T.; Werner, T.

2014-01-01

Roč. 78, č. 3 (2014), s. 359-371 ISSN 0960-7412 Institutional support: RVO:61389030 Keywords : xylem differentiation * Arabidopsis thaliana * cytokinin oxidase/dehydrogenase Subject RIV: ED - Physiology Impact factor: 5.972, year: 2014

Cytokinin Profiles of AtCKX2-Overexpressing Potato Plants and the Impact of Altered Cytokinin Homeostasis on Tuberization In Vitro

Czech Academy of Sciences Publication Activity Database

Raspor, M.; Motyka, Václav; Žižková, Eva; Dobrev, Petre; Trávníčková, Alena; Zdravkovic-Korac, S.; Simonovic, A.; Ninkovic, S.; Dragicevic, I. C.

2012-01-01

Roč. 31, č. 3 (2012), s. 460-470 ISSN 0721-7595 R&D Projects: GA ČR(CZ) GAP506/11/0774; GA MŠk(CZ) LC06034 Institutional research plan: CEZ:AV0Z50380511 Keywords : Bioactive cytokinins * Cytokinin oxidase/dehydrogenase (CKX) * In vitro Subject RIV: ED - Physiology Impact factor: 1.990, year: 2012

Solvent engineering and other reaction design methods for favouring enzyme-catalysed synthesis

DEFF Research Database (Denmark)

Zeuner, Birgitte

. However, both FAEs catalysed the feruloylation and/or sinapoylation of solvent cation C2OHMIm+, thus underlining the broad acceptor specificity of FAEs and their potential for future solvent reactions. An engineered sialidase from Trypanosoma rangeli, Tr6, catalyses trans-sialylation but the yield......This thesis investigates different methods for improving reaction yields of enzyme-catalysed synthesis reactions. These methods include the use of non-conventional media such as ionic liquids (ILs) and organic solvents as main solvents or as co-solvents as well as the use of more classical reaction...... design methods, i.e. enzyme immobilization and the use of an enzymatic membrane reactor. Two different enzyme classes, namely feruloyl esterases (FAEs) and sialidases are employed. Using sinapoylation of glycerol as a model reaction it was shown that both the IL anion nature and the FAE structure were...

Response of cytokinin pool and cytokinin oxidase/dehydrogenase activity to abscisic acid exhibits organ specificity in peas

Czech Academy of Sciences Publication Activity Database

Vaseva, I.; Todorova, D.; Malbeck, Jiří; Trávníčková, Alena; Macháčková, Ivana

2008-01-01

Roč. 30, č. 2 (2008), s. 151-155 ISSN 0137-5881 Institutional research plan: CEZ:AV0Z50380511 Keywords : Abscisic acid * Cytokinins * Cytokinin Subject RIV: EF - Botanics Impact factor: 0.807, year: 2008

Changes in cytokinin content and altered cytokinin homeostasis in AtCKX1 and AtCKX2-overexpressing centaury (Centaurium erythraea Rafn.) plants grown in vitro

Czech Academy of Sciences Publication Activity Database

Trifunovic, M.; Motyka, Václav; Cingel, A.; Subotic, A.; Jevremovic, S.; Petric, M.; Holík, Josef; Malbeck, Jiří; Dobrev, Petre; Dragicevic, I.

2015-01-01

Roč. 120, č. 2 (2015), s. 767-777 ISSN 0167-6857 R&D Projects: GA ČR(CZ) GAP506/11/0774 Institutional support: RVO:61389030 Keywords : Centaurium erythraea Rafn. * Cytokinin * Cytokinin oxidase/dehydrogenase Subject RIV: EF - Botanics Impact factor: 2.390, year: 2015

Control of cytokinin and auxin homeostasis in cyanobacteria and algae

Czech Academy of Sciences Publication Activity Database

Žižková, Eva; Kubeš, Martin; Dobrev, Petre; Přibyl, Pavel; Šimura, J.; Zahajská, Lenka; Záveská Drábková, Lenka; Novák, Ondřej; Motyka, Václav

2017-01-01

Roč. 119, č. 1 (2017), s. 151-166 ISSN 0305-7364 R&D Projects: GA ČR(CZ) GA16-14649S; GA ČR GA15-22322S; GA MŠk(CZ) LO1204 Institutional support: RVO:61389030 ; RVO:67985939 Keywords : solid-phase extraction * performance liquid-chromatography * yucca flavin monooxygenases * tandem mass-spectrometry * abscisic-acid * arabidopsis-thaliana * indole-3-acetic-acid iaa * endogenous cytokinins * chlorella-vulgaris * phenylacetic acid * Cytokinin * auxin * cyanobacteria * algae * metabolism * cytokinin oxidase/dehydrogenase * cytokinin 2-methylthioderivatives * trans-zeatin * indole-3-acetic acid * tRNA Subject RIV: EF - Botanics OBOR OECD: Plant sciences, botany Impact factor: 4.041, year: 2016

Genome-Wide Identification and Expression Profiling of Cytokinin Oxidase/Dehydrogenase (CKX) Genes Reveal Likely Roles in Pod Development and Stress Responses in Oilseed Rape (Brassica napus L.).

Science.gov (United States)

Liu, Pu; Zhang, Chao; Ma, Jin-Qi; Zhang, Li-Yuan; Yang, Bo; Tang, Xin-Yu; Huang, Ling; Zhou, Xin-Tong; Lu, Kun; Li, Jia-Na

2018-03-16

Cytokinin oxidase/dehydrogenases (CKXs) play a critical role in the irreversible degradation of cytokinins, thereby regulating plant growth and development. Brassica napus is one of the most widely cultivated oilseed crops worldwide. With the completion of whole-genome sequencing of B. napus , genome-wide identification and expression analysis of the BnCKX gene family has become technically feasible. In this study, we identified 23 BnCKX genes and analyzed their phylogenetic relationships, gene structures, conserved motifs, protein subcellular localizations, and other properties. We also analyzed the expression of the 23 BnCKX genes in the B. napus cultivar Zhong Shuang 11 ('ZS11') by quantitative reverse-transcription polymerase chain reaction (qRT-PCR), revealing their diverse expression patterns. We selected four BnCKX genes based on the results of RNA-sequencing and qRT-PCR and compared their expression in cultivated varieties with extremely long versus short siliques. The expression levels of BnCKX5-1 , 5-2 , 6-1 , and 7-1 significantly differed between the two lines and changed during pod development, suggesting they might play roles in determining silique length and in pod development. Finally, we investigated the effects of treatment with the synthetic cytokinin 6-benzylaminopurine (6-BA) and the auxin indole-3-acetic acid (IAA) on the expression of the four selected BnCKX genes. Our results suggest that regulating BnCKX expression is a promising way to enhance the harvest index and stress resistance in plants.

Natural spectroscopic hydrogen isotope transfer in alcohol dehydrogenase-catalysed reduction

International Nuclear Information System (INIS)

Ben-Li Zhang; Pionnier, S.

2002-01-01

The enantiomeric purity of natural α-mono deuterated enantiomers, (R) and (S)ethanol-1-d 1 , in the alcohol produced by sugar fermentation with yeast was studied by 2 H NMR using their esters derived from optical mandelic acid. The results of isotope tracing experiments show that the transfer pathways of the two eantiotopic hydrogens of the methylene group are different. It was observed that (S)-deuterium comes only from the medium water. The (R)-deuterium transferred by NADH in alcohol dehydrogenase reduction of the acetaldehyde is complex origin. Some of them originates from carbon bound hydrogen of the sugar, especially from C(4) position of glucose and most of them comes from water. Only a small portion of the NADH deuterium is incorporated indirectly from water through enzyme catalysed exchange between the pro-S site of NADH and flavin. When a carbonyl compound (ethyl acetoacetate) was reduced under the same conditions during the alcoholic fermentation, among the NADH-transferred deuterium, only a small portion comes from water while most comes from the unexchangeable positions of the glucose. (author)

Kinetics and mechanism of the base-catalysed reaction of 4 ...

African Journals Online (AJOL)

NPMPF) in benzene has been investigated at 27oC and in the presence of functionally similar, but structurally different addenda, namely; imidazole, pyridine and triethylamine. The reaction is catalysed by the nucleophile and imidazole in a linear ...

Heterogeneously Catalysed Chemical Reactions in Carbon Dioxide Medium

DEFF Research Database (Denmark)

Musko, Nikolai E.

In this PhD-study the different areas of chemical engineering, heterogeneous catalysis, supercritical fluids, and phase equilibrium thermodynamics have been brought together for selected reactions. To exploit the beneficial properties of supercritical fluids in heterogeneous catalysis, experimental...... studies of catalytic chemical reactions in dense and supercritical carbon dioxide have been complemented by the theoretical calculations of phase equilibria using advanced thermodynamic models. In the recent years, the use of compressed carbon dioxide as innovative, non-toxic and non-flammable, cheap......, and widely available reaction medium for many practical and industrial applications has drastically increased. Particularly attractive are heterogeneously catalysed chemical reactions. The beneficial use of CO2 is attributed to its unique properties at dense and supercritical states (at temperatures...

Prussian Blue acts as a mediator in a reagentless cytokinin biosensor

International Nuclear Information System (INIS)

Kowalska, Marta; Tian Faming; Smehilova, Maria; Galuszka, Petr; Frebort, Ivo; Napier, Richard; Dale, Nicholas

2011-01-01

Highlights: · An electrochemical biosensor for detection of the plant hormone cytokinin. · Constitutive expression system for large-scale protein production. · CKX enzyme entrapment in sol-gel film on the surface of a PrB-modified electrode. · Prussian Blue as an electron mediator between the enzyme and the electrode. · The biosensor was sensitive to micromolar concentrations of several cytokinins. - Abstract: An electrochemical biosensor for detection of the plant hormone cytokinin is introduced. Cytokinin homeostasis in tissues of many lower and higher plants is controlled largely by the activity of cytokinin dehydrogenase (CKX, EC 1.5.99.12) that catalyzes an irreversible cleavage of N 6 -side chain of cytokinins. Expression of Arabidopsis thaliana CKX2 from Pichia pastoris was used to prepare purified AtCKX2 as the basis of the cytokinin biosensor. Prussian Blue (PrB) was electrodeposited on Pt microelectrodes prior to deposition of the enzyme in a sol-gel matrix. The biosensor gave amperometric responses to several cytokinins. These responses depended on the presence of both the enzyme and the Prussian Blue. Thus Prussian Blue must act as an electron mediator between the FAD centre in CKX2 and the Pt surface.

SAM-dependent enzyme-catalysed pericyclic reactions in natural product biosynthesis

Science.gov (United States)

Ohashi, Masao; Liu, Fang; Hai, Yang; Chen, Mengbin; Tang, Man-Cheng; Yang, Zhongyue; Sato, Michio; Watanabe, Kenji; Houk, K. N.; Tang, Yi

2017-09-01

Pericyclic reactions—which proceed in a concerted fashion through a cyclic transition state—are among the most powerful synthetic transformations used to make multiple regioselective and stereoselective carbon-carbon bonds. They have been widely applied to the synthesis of biologically active complex natural products containing contiguous stereogenic carbon centres. Despite the prominence of pericyclic reactions in total synthesis, only three naturally existing enzymatic examples (the intramolecular Diels-Alder reaction, and the Cope and the Claisen rearrangements) have been characterized. Here we report a versatile S-adenosyl-L-methionine (SAM)-dependent enzyme, LepI, that can catalyse stereoselective dehydration followed by three pericyclic transformations: intramolecular Diels-Alder and hetero-Diels-Alder reactions via a single ambimodal transition state, and a retro-Claisen rearrangement. Together, these transformations lead to the formation of the dihydropyran core of the fungal natural product, leporin. Combined in vitro enzymatic characterization and computational studies provide insight into how LepI regulates these bifurcating biosynthetic reaction pathways by using SAM as the cofactor. These pathways converge to the desired biosynthetic end product via the (SAM-dependent) retro-Claisen rearrangement catalysed by LepI. We expect that more pericyclic biosynthetic enzymatic transformations remain to be discovered in naturally occurring enzyme ‘toolboxes’. The new role of the versatile cofactor SAM is likely to be found in other examples of enzyme catalysis.

Regioselectivity and Enantioselectivity in Nickel-Catalysed Reductive Coupling Reactions of Alkynes

Science.gov (United States)

Moslin, Ryan M.; Miller-Moslin, Karen; Jamison, Timothy F.

2011-01-01

Nickel-catalysed reductive coupling reactions of alkynes have emerged as powerful synthetic tools for the selective preparation of functionalized alkenes. One of the greatest challenges associated with these transformations is control of regioselectivity. Recent work from our laboratory has provided an improved understanding of several of the factors governing regioselectivity in these reactions, and related studies have revealed that the reaction mechanism can differ substantially depending on the ligand employed. A discussion of stereoselective transformations and novel applications of nickel catalysis in coupling reactions of alkynes is also included. PMID:17971951

Genome-wide analysis and identification of cytokinin oxidase/dehydrogenase (CKX gene family in foxtail millet (Setaria italica

Directory of Open Access Journals (Sweden)

Yuange Wang

2014-08-01

Full Text Available Cytokinin oxidase/dehydrogenase (CKX; EC.1.5.99.12 regulates cytokinin (CK level in plants and plays an essential role in CK regulatory processes. CKX proteins are encoded by a small gene family with a varying number of members in different plants. In spite of their physiological importance, systematic analyses of SiCKX genes in foxtail millet have not yet been examined. In this paper, we report the genome wide isolation and characterization of SiCKXs using bioinformatic methods. A total of 11 members of the family were identified in the foxtail millet genome. SiCKX genes were distributed in seven chromosomes (chromosome 1, 3, 4, 5, 6, 7, and 11. The coding sequences of all the SiCKX genes were disrupted by introns, with numbers varying from one to four. These genes expanded in the genome mainly due to segmental duplication events. Multiple alignment and motif display results showed that all SiCKX proteins share FAD- and CK-binding domains. Putative cis-elements involved in Ca2 +-response, abiotic stress response, light and circadian rhythm regulation, disease resistance and seed development were present in the promoters of SiCKX genes. Expression data mining suggested that SiCKX genes have diverse expression patterns. Real-time PCR analysis indicated that all 11 SiCKX genes were up-regulated in embryos under 6-BA treatment, and some were NaCl or PEG inducible. Collectively, these results provide molecular insights into CKX research in plants.

Carbene Transfer Reactions Catalysed by Dyes of the Metalloporphyrin Group

Directory of Open Access Journals (Sweden)

Mário M. Q. Simões

2018-03-01

Full Text Available Carbene transfer reactions are very important transformations in organic synthesis, allowing the generation of structurally challenging products by catalysed cyclopropanation, cyclopropenation, carbene C-H, N-H, O-H, S-H, and Si-H insertion, and olefination of carbonyl compounds. In particular, chiral and achiral metalloporphyrins have been successfully explored as biomimetic catalysts for these carbene transfer reactions under both homogeneous and heterogeneous conditions. In this work the use of synthetic metalloporphyrins (MPorph, M = Fe, Ru, Os, Co, Rh, Ir, Sn as homogeneous or heterogeneous catalysts for carbene transfer reactions in the last years is reviewed, almost exclusively focused on the literature since the year 2010, except when reference to older publications was deemed to be crucial.

Chemoselective N-arylation of aminobenzamides via copper catalysed Chan-Evans-Lam reactions.

Science.gov (United States)

Liu, Shuai; Zu, Weisai; Zhang, Jinli; Xu, Liang

2017-11-15

Chemoselective N-arylation of unprotected aminobenzamides was achieved via Cu-catalysed Chan-Evans-Lam cross-coupling with aryl boronic acids for the first time. Simple copper catalysts enable the selective arylation of amino groups in ortho/meta/para-aminobenzamides under open-flask conditions. The reactions were scalable and compatible with a wide range of functional groups.

Total syntheses of mitragynine, paynantheine and speciogynine via an enantioselective thiourea-catalysed Pictet-Spengler reaction

NARCIS (Netherlands)

Kerschgens, I. P.; Claveau, E.; Wanner, M.J.; Ingemann, S.; van Maarseveen, J.H.; Hiemstra, H.

2012-01-01

The pharmacologically interesting indole alkaloids (-)-mitragynine, (+)-paynantheine and (+)-speciogynine were synthesised in nine steps from 4-methoxytryptamine by a route featuring (i) an enantioselective thiourea-catalysed Pictet-Spengler reaction, providing the tetrahydro-β-carboline ring and

Determination of the in vivo NAD:NADH ratio in Saccharomyces cerevisiae under anaerobic conditions, using alcohol dehydrogenase as sensor reaction.

Science.gov (United States)

Bekers, K M; Heijnen, J J; van Gulik, W M

2015-08-01

With the current quantitative metabolomics techniques, only whole-cell concentrations of NAD and NADH can be quantified. These measurements cannot provide information on the in vivo redox state of the cells, which is determined by the ratio of the free forms only. In this work we quantified free NAD:NADH ratios in yeast under anaerobic conditions, using alcohol dehydrogenase (ADH) and the lumped reaction of glyceraldehyde-3-phosphate dehydrogenase and 3-phosphoglycerate kinase as sensor reactions. We showed that, with an alternative accurate acetaldehyde determination method, based on rapid sampling, instantaneous derivatization with 2,4 diaminophenol hydrazine (DNPH) and quantification with HPLC, the ADH-catalysed oxidation of ethanol to acetaldehyde can be applied as a relatively fast and simple sensor reaction to quantify the free NAD:NADH ratio under anaerobic conditions. We evaluated the applicability of ADH as a sensor reaction in the yeast Saccharomyces cerevisiae, grown in anaerobic glucose-limited chemostats under steady-state and dynamic conditions. The results found in this study showed that the cytosolic redox status (NAD:NADH ratio) of yeast is at least one order of magnitude lower, and is thus much more reduced, under anaerobic conditions compared to aerobic glucose-limited steady-state conditions. The more reduced state of the cytosol under anaerobic conditions has major implications for (central) metabolism. Accurate determination of the free NAD:NADH ratio is therefore of importance for the unravelling of in vivo enzyme kinetics and to judge accurately the thermodynamic reversibility of each redox reaction. Copyright © 2015 John Wiley & Sons, Ltd.

Degradation of cytokinins by maize cytokinin dehydrogenase is mediated by free radicals generated by enzymatic oxidation of natural benzoxazinones

Czech Academy of Sciences Publication Activity Database

Frébortová, Jitka; Novák, Ondřej; Frébort, Ivo; Jorda, Radek

2010-01-01

Roč. 61, č. 3 (2010), s. 467-481 ISSN 0960-7412 R&D Projects: GA ČR GA522/05/0448; GA ČR GA301/08/1649 Institutional research plan: CEZ:AV0Z50380511 Keywords : Degradation * cytokinins * maize Subject RIV: EF - Botanics Impact factor: 6.948, year: 2010

Enhanced drought and heat stress tolerance of tobacco plants with ectopically enhanced cytokinin oxidase/dehydrogenase gene expression

Czech Academy of Sciences Publication Activity Database

Macková, Hana; Hronková, Marie; Dobrá, Jana; Turečková, Veronika; Novák, Ondřej; Lubovská, Zuzana; Motyka, Václav; Haisel, Daniel; Hájek, Tomáš; Prášil, I.T.; Gaudinová, Alena; Štorchová, Helena; Ge, Eva; Werner, T.; Schmülling, T.; Vaňková, Radomíra

2013-01-01

Roč. 64, č. 10 (2013), s. 2805-2815 ISSN 0022-0957 R&D Projects: GA ČR GA206/09/2062 Institutional support: RVO:61389030 ; RVO:60077344 ; RVO:67985939 Keywords : cytokinin oxidase * cytokinin * Abscisic acid Subject RIV: ED - Physiology Impact factor: 5.794, year: 2013

Synthesis of a Cytokinin Linked by a Spacer to Dexamethasone and Biotin: Conjugates to Detect Cytokinin-Binding Proteins

Directory of Open Access Journals (Sweden)

You Wang

2016-04-01

Full Text Available Yeast cells expressing cDNA libraries have provided two new approaches to facilitate further identification of cytokinin-binding proteins and receptors. These are the yeast three hybrid (Y3H system and fluorescence activated cell sorting (FACS. The Y3H system requires a synthetic hybrid ligand comprising an “anchor” moiety (e.g., dexamethasone linked to a cytokinin via a spacer. In the yeast nucleus, this ligand by binding connects two fusion proteins leading to a reporter gene activation and detection and characterisation of cytokinin binding proteins. Herein is reported the first synthesis of dexamethasone-cytokinin ligands with a spacer linkage. This was attached to the purine ring of 6-benzylaminopurine (BAP at positions 2, 8 or 9. To achieve this, dexamethasone was modified by periodate oxidation yielding a carboxylic group used for conjugation to the spacer by amide formation. Biotinyl derivatives of cytokinins for FACS included those synthesised by reaction of an activated ester of biotin with 8-(10-amino-decylamino derivatives of BAP and BAP 9-riboside. Properties of the conjugates and some biological situations where they could be applicable are discussed briefly.

Kinetics based reaction optimization of enzyme catalysed reduction of formaldehyde to methanol with synchronous cofactor regeneration

DEFF Research Database (Denmark)

Marpani, Fauziah Binti; Sárossy, Zsuzsa; Pinelo, Manuel

2017-01-01

regeneration of the reducing equivalents during reaction is required. Herein, we report the optimization of the enzymatic conversion of formaldehyde (CHOH) to CH3 OH by alcohol dehydrogenase, the final step of the enzymatic redox reaction of CO2 to CH3 OH, with kinetically synchronous enzymatic cofactor...... regeneration using either glucose dehydrogenase (System I) or xylose dehydrogenase (System II). A mathematical model of the enzyme kinetics was employed to identify the best reaction set-up for attaining optimal cofactor recycling rate and enzyme utilization efficiency. Targeted process optimization...... experiments were conducted to verify the kinetically modelled results. Repetitive reaction cycles were shown to enhance the yield of CH3 OH, increase the total turnover number (TTN) and the biocatalytic productivity rate (BPR) value for both system I and II whilst minimizing the exposure of the enzymes...

Photosynthesis and protective mechanisms during ageing in transgenic tobacco leaves with over-expressed cytokinin oxidase/dehydrogenase and thus lowered cytokinin content

Czech Academy of Sciences Publication Activity Database

Mýtinová, Zuzana; Haisel, Daniel; Wilhelmová, Naděžda

2006-01-01

Roč. 44, č. 4 (2006), s. 599-605 ISSN 0300-3604 R&D Projects: GA ČR GA522/03/0312 Institutional research plan: CEZ:AV0Z50380511 Keywords : senescence * cytokinins * carotenoids * chlorophyll * xanthophylls cycle * photosynthetic efficiency * chlorophyll fluorescence * tobacco Subject RIV: CE - Biochemistry Impact factor: 0.782, year: 2006

Cytokinins in macroalgae

Czech Academy of Sciences Publication Activity Database

Stirk, W. A.; Novák, Ondřej; Strnad, Miroslav; Staden, J.

2003-01-01

Roč. 41, č. 1 (2003), s. 13-24 ISSN 0167-6903 R&D Projects: GA ČR GA522/03/0323 Institutional research plan: CEZ:AV0Z5038910; CEZ:MSM 153100008 Keywords : Aromatic cytokinins * Cytokinin content * Isoprenoid cytokinins Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 0.688, year: 2003

[Facultative and obligate aerobic methylobacteria synthesize cytokinins].

Science.gov (United States)

Ivanova, E G; Doronina, N V; Shepeliakovskaia, A O; Laman, A G; Brovko, F A; Trotsenko, Iu A

2000-01-01

The presence and expression of genes controlling the synthesis and secretion of cytokinins by the pink-pigmented facultative methylotroph Methylobacterium mesophilicum VKM B-2143 with the serine pathway and nonpigmented obligate methylotroph Methylovorus mays VKM B-2221 with the ribulose monophosphate pathway of C1 metabolism were shown using the polymerase chain reaction (PCR) and reverse transcription-PCR methods. The presence of the corresponding mRNA in M. mesophilicum cells grown on methanol or succinate suggests that the expression of these genes is constitutive. The cytokinin activity of culture liquid and its fractions was determined by a biotest with Amarantus caudatus L. seedlings. Using enzyme-linked immunosorbent analysis, we detected zeatin (riboside) in the culture liquid of both bacteria studied. The data obtained show that the aerobic methylobacteria are phytosymbionts that are able to utilize the single- and polycarbon compounds secreted by symbiotic plants and to synthesize cytokinins.

Zeolite and zeotype-catalysed transformations of biofuranic compounds

DEFF Research Database (Denmark)

Li, Hu; Yang, Song; Riisager, Anders

2016-01-01

,5-furandicarboxylic acid can be obtained from hexoses and pentoses via selective dehydration and subsequent etherification, hydrogenation, oxidation reactions, which show great potential for industrial applications to replace petroleum-based chemicals and fuels. Zeolite and zeotype micro- and mesoporous materials...... with tuneable acidity, good thermal stability and shape-selectivity have recently emerged as promising solid catalysts, exhibiting superior catalytic performance to other heterogeneous catalysts. This review focuses on the synthesis of biomass-derived furanic compounds catalysed by zeolitic materials, firstly...... introducing zeolite-catalysed hydrolysis of di-, oligo- and polysaccharides and isomerization reactions of monomeric sugars. Subsequently, the catalytic dehydration reactions of hexoses and pentoses to obtain HMF and furfural are reported. Particularly, a variety of reaction pathways towards upgrading...

Coulometric bioelectrocatalytic reactions based on NAD-dependent dehydrogenases in tricarboxylic acid cycle

Energy Technology Data Exchange (ETDEWEB)

Fukuda, Jun [Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan); Tsujimura, Seiya [Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan)], E-mail: seiya@kais.kyoto-u.ac.jp; Kano, Kenji [Division of Applied Life Sciences, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-8502 (Japan)], E-mail: kkano@kais.kyoto-u.ac.jp

2008-12-30

This paper describes the characterization of mediated electro-enzymatic electrolysis systems based on NAD-dependent dehydrogenase reactions in the tricarboxylic acid (TCA) cycle. A micro-bulk electrolysis system with a carbon felt anode immersed in an electrolysis solution with a value of about 10 {mu}L was constructed for coulometric analysis of the substrate oxidation. Diaphorase (DI) was used to couple the NAD-dependent dehydrogenase reaction with the anode reaction of a suitable redox mediator. We focused on three types of NAD-dependant dehydrogenases reactions in this research: (1) isocitrate oxidation, in which the standard Gibbs energy change ({delta}G{sup o}') is negative; (2) {alpha}-ketoglutarate oxidation, which involves an electrochemically active coenzyme A (CoA); and (3) malate oxidation, which is thermodynamically unfavorable because of a large positive {delta}G{sup o}' value. The complete electrolysis of isocitrate was easily achieved, supporting the effective re-oxidation of NADH in the diaphorase-catalyzed electrochemical reaction. CoA was unfavorably oxidized at the electrodes in the presence of some mediators. The electrocatalytic oxidation of CoA was suppressed and the quantitative electrochemical oxidation of {alpha}-ketoglutarate was achieved by selecting a suitable mediator with negligibly slow electron transfer kinetics with CoA. The uphill malate oxidation was susceptible to product inhibition in the bioelectrochemical system, although NADH generated in the malate dehydrogenase reaction was immediately oxidized in the electrochemical system. The inhibition was successfully suppressed by linking citrate synthase to quench oxaloacetate and to make the total {delta}G{sup o}' value negative.

Coulometric bioelectrocatalytic reactions based on NAD-dependent dehydrogenases in tricarboxylic acid cycle

International Nuclear Information System (INIS)

Fukuda, Jun; Tsujimura, Seiya; Kano, Kenji

2008-01-01

This paper describes the characterization of mediated electro-enzymatic electrolysis systems based on NAD-dependent dehydrogenase reactions in the tricarboxylic acid (TCA) cycle. A micro-bulk electrolysis system with a carbon felt anode immersed in an electrolysis solution with a value of about 10 μL was constructed for coulometric analysis of the substrate oxidation. Diaphorase (DI) was used to couple the NAD-dependent dehydrogenase reaction with the anode reaction of a suitable redox mediator. We focused on three types of NAD-dependant dehydrogenases reactions in this research: (1) isocitrate oxidation, in which the standard Gibbs energy change (ΔG o ') is negative; (2) α-ketoglutarate oxidation, which involves an electrochemically active coenzyme A (CoA); and (3) malate oxidation, which is thermodynamically unfavorable because of a large positive ΔG o ' value. The complete electrolysis of isocitrate was easily achieved, supporting the effective re-oxidation of NADH in the diaphorase-catalyzed electrochemical reaction. CoA was unfavorably oxidized at the electrodes in the presence of some mediators. The electrocatalytic oxidation of CoA was suppressed and the quantitative electrochemical oxidation of α-ketoglutarate was achieved by selecting a suitable mediator with negligibly slow electron transfer kinetics with CoA. The uphill malate oxidation was susceptible to product inhibition in the bioelectrochemical system, although NADH generated in the malate dehydrogenase reaction was immediately oxidized in the electrochemical system. The inhibition was successfully suppressed by linking citrate synthase to quench oxaloacetate and to make the total ΔG o ' value negative

Cytokinin oxidase from Phaseolus vulgaris callus tissues. Enhanced in vitro activity of the enzyme in the presence of copper-imidazole complexes

International Nuclear Information System (INIS)

Chatfield, J.M.; Armstrong, D.J.

1987-01-01

The effects of metal ions on cytokinin oxidase activity extracted from callus tissues of Phaseolus vulgaris L. cv Great Northern have been examined using an assay based on the oxidation of N 6 -(Δ 2 -isopentenyl)-adenine-2,8- 3 H (i 6 Ade) to adenine (Ade). The addition of cupric ions to reaction mixtures containing imidazole buffer markedly enhanced cytokinin oxidase activity. In the presence of optimal concentrations of copper and imidazole, cytokinin oxidase activity was stimulated more than 20-fold. The effect was enzyme dependent, specific for copper, and observed only in the presence of imidazole. The substrate specificity of the copper-imidazole enhanced reaction, as judged by substrate competition tests, was the same as that observed in the absence of copper and imidazole. Similarly, in tests involving DEAE-cellulose chromatography, elution profiles of cytokinin oxidase activity determined using a copper-imidazole enhanced assay were identical to those obtained using an assay without copper and imidazole. On the basis of these results, the addition of copper and imidazole to reaction mixtures used to assay for cytokinin oxidase activity is judged to provide a reliable and specific assay of greatly enhanced sensitivity for the enzyme. The mechanism by which copper and imidazole enhance cytokinin oxidase activity is not certain, but the reaction catalyzed by the enzyme was not inhibited by anaerobic conditions when these reagents were present. This observation suggests that copper-imidazole complexes are substituting for oxygen in the reaction mechanism by which cytokinin oxidase effects cleavage of the N 6 -side chain of i 6 Ade

Enzyme dynamics and hydrogen tunnelling in a thermophilic alcohol dehydrogenase

Science.gov (United States)

Kohen, Amnon; Cannio, Raffaele; Bartolucci, Simonetta; Klinman, Judith P.; Klinman, Judith P.

1999-06-01

Biological catalysts (enzymes) speed up reactions by many orders of magnitude using fundamental physical processes to increase chemical reactivity. Hydrogen tunnelling has increasingly been found to contribute to enzyme reactions at room temperature. Tunnelling is the phenomenon by which a particle transfers through a reaction barrier as a result of its wave-like property. In reactions involving small molecules, the relative importance of tunnelling increases as the temperature is reduced. We have now investigated whether hydrogen tunnelling occurs at elevated temperatures in a biological system that functions physiologically under such conditions. Using a thermophilic alcohol dehydrogenase (ADH), we find that hydrogen tunnelling makes a significant contribution at 65°C this is analogous to previous findings with mesophilic ADH at 25°C ( ref. 5). Contrary to predictions for tunnelling through a rigid barrier, the tunnelling with the thermophilic ADH decreases at and below room temperature. These findings provide experimental evidence for a role of thermally excited enzyme fluctuations in modulating enzyme-catalysed bond cleavage.

Physiological responses and endogenous cytokinin profiles of tissue-cultured 'Williams' bananas in relation to roscovitine and an inhibitor of cytokinin oxidase/dehydrogenase (INCYDE) treatments

Czech Academy of Sciences Publication Activity Database

Aremu, A.O.; Bairu, M. W.; Novák, Ondřej; Plačková, Lenka; Zatloukal, Marek; Doležal, Karel; Finnie, J.F.; Strnad, Miroslav; van Staden, J.

2012-01-01

Roč. 236, č. 6 (2012), s. 1775-1790 ISSN 0032-0935 Grant - others:GA MŠk(CZ) ED0007/01/01 Program:ED Institutional research plan: CEZ:AV0Z50380511 Keywords : Cyclin-dependent kinase * Cytokinin metabolism * Micropropagation Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.347, year: 2012

Recent Advances in the Synthesis of N-Containing Heteroaromatics via Heterogeneously Transition Metal Catalysed Cross-Coupling Reactions

Directory of Open Access Journals (Sweden)

Laurent Djakovitch

2011-06-01

Full Text Available N-containing heteroaromatics are important substructures found in numerous natural or synthetic alkaloids. The diversity of the structures encountered, as well as their biological and pharmaceutical relevance, have motivated research aimed at the development of new economical, efficient and selective synthetic strategies to access these compounds. Over more than 100 years of research, this hot topic has resulted in numerous so-called “classical synthetic methods” that have really contributed to this important area. However, when the selective synthesis of highly functional heteroaromatics like indoles, quinolones, indoxyls, etc. is considered these methods remain limited. Recently transition metal-catalysed (TM-catalysed procedures for the synthesis of such compounds and further transformations, have been developed providing increased tolerance toward functional groups and leading generally to higher reaction yields. Many of these methods have proven to be the most powerful and are currently applied in target- or diversity-oriented syntheses. This review article aims at reporting the recent developments devoted to this important area, focusing on the use of heterogeneous catalysed procedures that include either the formation of the heterocyclic ring towards the nuclei or their transformations to highly substituted compounds.

The base catalysed hydrolysis of methyl paraben: a test reaction for flow microcalorimeters used for determination of both kinetic and thermodynamic parameters

Energy Technology Data Exchange (ETDEWEB)

O' Neill, M.A.A.; Beezer, A.E.; Labetoulle, C.; Nicolaides, L.; Mitchell, J.C.; Orchard, J.A.; Connor, J.A.; Kemp, R.B.; Olomolaiye, D

2003-03-24

The results of an inter/intra-laboratory study into a test and reference reaction for isothermal microcalorimeters, the imidazole catalysed hydrolysis of triacetin, have been reported in a recent paper [Thermochim. Acta 380 (2001) 13]. The results and conclusions drawn from this study have been extended to a consideration of the need for a similar test and reference reaction for isothermal microcalorimeters operating in flow mode. This paper reports the findings of a preliminary inter/intra-laboratory study of the base catalysed hydrolysis of methyl 4-hydroxy benzoate (methyl paraben) and its suitability as a test and reference reaction. The derived values for the hydrolysis reaction were (3.15{+-}0.11)x10{sup -4} s{sup -1} and -50.5{+-}4.3 kJ mol{sup -1} for the rate constant and enthalpy, respectively. It is also reported how such a test and reference reaction can be used to validate the thermal output from a LKB 10-700-1 and Thermometric Thermal Activity Monitor (TAM) 2277-202 flow microcalorimeters.

C-13 isotopic studies of the surface catalysed reactions of methane

International Nuclear Information System (INIS)

Long, M.A.; He, S.J.X.; Adebajo, M.

1997-01-01

The ability of methane to methylate aromatic compounds, which are considered to be models for coal, is being studied. Related to this reaction, but at higher temperatures, is the direct formation of benzene from methane in the presence of these catalysts. Controversy exists in the literature on the former reaction, and 13 C isotope studies are being used to resolve the question. The interest in this reaction arises because the utilisation of methane, in the form of natural gas, in place of hydrogen for direct coal liquefaction would have major economic advantage. For this reason Isotope studies in this area have contributed significantly to an understanding of the methylation reactions. The paper describes experiments utilising methane 13 C, which show that methylation of aromatics such as naphthalene by the methane 13 C is catalysed by microporous, Cu-exchanged SAPO-5, at elevated pressures (6.8 MPa) and temperatures around 400 degree C. The mass spectrometric analysis and n.m.r. study of the isotopic composition of the products of the methylation reaction demonstrate unequivocally that methane provides the additional carbon atom for the methylated products. Thermodynamic calculations predict that the reaction is favourable at high methane pressures under these experimental conditions. The mechanism as suggested by the isotope study is discussed. The catalysts which show activity for the activation of methane for direct methylation of organic compounds, such as naphthalene, toluene, phenol and pyrene, are substituted aluminophosphate molecular sieves, EIAPO-5 (where El=Pb, Cu, Ni and Si) and a number of metal substituted zeolites. Our earlier tritium studies had shown that these catalysts will activate alkanes, at least as far as isotope hydrogen exchange reactions are concerned

Identification of cytokinin-responsive genes using microarray meta-analysis and RNA-Seq in Arabidopsis.

Science.gov (United States)

Bhargava, Apurva; Clabaugh, Ivory; To, Jenn P; Maxwell, Bridey B; Chiang, Yi-Hsuan; Schaller, G Eric; Loraine, Ann; Kieber, Joseph J

2013-05-01

Cytokinins are N(6)-substituted adenine derivatives that play diverse roles in plant growth and development. We sought to define a robust set of genes regulated by cytokinin as well as to query the response of genes not represented on microarrays. To this end, we performed a meta-analysis of microarray data from a variety of cytokinin-treated samples and used RNA-seq to examine cytokinin-regulated gene expression in Arabidopsis (Arabidopsis thaliana). Microarray meta-analysis using 13 microarray experiments combined with empirically defined filtering criteria identified a set of 226 genes differentially regulated by cytokinin, a subset of which has previously been validated by other methods. RNA-seq validated about 73% of the up-regulated genes identified by this meta-analysis. In silico promoter analysis indicated an overrepresentation of type-B Arabidopsis response regulator binding elements, consistent with the role of type-B Arabidopsis response regulators as primary mediators of cytokinin-responsive gene expression. RNA-seq analysis identified 73 cytokinin-regulated genes that were not represented on the ATH1 microarray. Representative genes were verified using quantitative reverse transcription-polymerase chain reaction and NanoString analysis. Analysis of the genes identified reveals a substantial effect of cytokinin on genes encoding proteins involved in secondary metabolism, particularly those acting in flavonoid and phenylpropanoid biosynthesis, as well as in the regulation of redox state of the cell, particularly a set of glutaredoxin genes. Novel splicing events were found in members of some gene families that are known to play a role in cytokinin signaling or metabolism. The genes identified in this analysis represent a robust set of cytokinin-responsive genes that are useful in the analysis of cytokinin function in plants.

Dipeptide catalysed prebiotic polymerization of RNA

DEFF Research Database (Denmark)

Wieczorek, Rafal; Luisi, Pier Luigi; Monnard, Pierre-Alain

2011-01-01

toward more peptide synthesis. In the present work we describe a prebiotically plausible system in which the SerHis dipeptide acts as catalyst for the formation of RNA oligomers from imidazole derivatives of mononucleotides. The thermodynamic shift towards condensation was achieved using water...... be an important factor from an origin-of-life point of view. Short peptides are plausible products of prebiotic chemistry2. Consequently, they could have influenced chemical evolution on an early stage. An enzyme catalysing hydrolytic reactions can in principle be used as catalyst for condensation: the reverse......-concentrated in the remaining liquid microinclusions, thus creating an environment with low water activity in which condensation reactions can occur. Successful oligomerization of RNA monomers catalysed by the SerHis dipeptide was observed in a broad range of pH, and with all four natural nucleobases. The isomeric dipeptide...

Hemicellulose hydrolysis catalysed by solid acids

NARCIS (Netherlands)

Carà, P.D.; Pagliaro, M.; Elmekawy, A.; Brown, D.R.; Verschuren, P.; Shiju, N.R.; Rothenberg, G.

2013-01-01

Depolymerising hemicellulose into platform sugar molecules is a key step in developing the concept of an integrated biorefinery. This reaction is traditionally catalysed by either enzymes or homogeneous mineral acids. We compared various solid catalysts for hemicellulose hydrolysis, running

A novel reaction catalysed by active carbons production of dichloromethane from phosgene and formaldehyde

Energy Technology Data Exchange (ETDEWEB)

Ryan, T A; Stacey, M H

1984-08-01

A variety of Activated charcoals have been found to catalyse a reaction between phosgene and formaldehyde. In a continuous flow fluidized bed reactor, the reaction rate reaches a broad maximum near 170/sup 0/C where the selectivity is consistent with the stoichiometry. The reaction proceeds via a strongly adsorbed intermediate which has been identified as chloromethyl chloroformate. This ester is an adduct of formaldehyde and phosgen and forms rapidly above 100/sup 0/C in co-adsorption/desorption experiments. It decomposes rapidly 170/sup 0/C without significant desorption of the intact molecule to give the observed products dichloromethane and carbon dioxide. Under steady-state conditions the rate-determining step is the formation of this ester so that it is normally only present on the surface at low coverages; hence it is not observable in the gas phase. The catalysis is probably due to the presence of polar acid or base sites on the surface of the activated charcoals.

A hydrogen fuel cell for rapid, enzyme-catalysed organic synthesis with continuous monitoring.

Science.gov (United States)

Wan, Lei; Megarity, Clare F; Siritanaratkul, Bhavin; Armstrong, Fraser A

2018-01-23

A one-pot fuel cell for specific, enzyme-catalysed organic synthesis, with continuous monitoring of rate and reaction progress, combines an electrode catalysing rapid, reversible and diffusion-controlled interconversion of NADP + and NADPH with a Pt electrode catalysing 2H + /H 2 interconversion. This Communication demonstrates its performance and characteristics using the reductive amination of 2-oxoglutarate as a test system.

Involvement of cis-Zeatin, Dihydrozeatin, and Aromatic Cytokinins in Germination and Seedling Establishment of Maize, Oats, and Lucerne

Czech Academy of Sciences Publication Activity Database

Stirk, W. A.; Václavíková, Kateřina; Novák, Ondřej; Gajdošová, Silvia; Kotland, O.; Motyka, Václav; Strnad, Miroslav; van Staden, J.

2012-01-01

Roč. 31, č. 3 (2012), s. 392-405 ISSN 0721-7595 R&D Projects: GA MŠk(CZ) LC06034; GA ČR(CZ) GAP506/11/0774 Grant - others:GA MŠk(CZ) ED0007/01/01 Program:ED Institutional research plan: CEZ:AV0Z50380511 Keywords : cis-Zeatin * cytokinin oxidase/dehydrogenase * dihydrozeatin Subject RIV: EF - Botanics Impact factor: 1.990, year: 2012

Efficient one-pot enzymatic synthesis of alpha-(1 -> 4)-glucosidic disaccharides through a coupled reaction catalysed by Lactobacillus acidophilus NCFM maltose phosphorylase

DEFF Research Database (Denmark)

Nakai, Hiroyuki; Dilokpimol, Adiphol; Abou Hachem, Maher

2010-01-01

Lactobacillus acidophilus NCFM maltose phosphorylase (LaMalP) of glycoside hydrolase family 65 catalysed enzymatic synthesis of alpha-(1 -> 4)-glucostdic disacchandes from maltose and five monosacchandes in a coupled phosphorolysis/reverse phosphorolysis one-pot reaction Thus phosphorolysis...

Solution structures of lipoyl domains of the 2-oxo acid dehydrogenase complexes from Azotobacter vinelandii : implications for molecular recognition

NARCIS (Netherlands)

Berg, A.

1997-01-01

The 2-oxo acid dehydrogenase complexes are large multienzyme complexes that catalyse the irreversible oxidative decarboxylation of a specific 2-oxo acid to the corresponding acyl-CoA derivative. The pyruvate dehydrogenase complex (PDHC) converts the product of the glycolysis, pyruvate, to

Palladium-catalysed cyclisation of alkenols: Synthesis of oxaheterocycles as core intermediates of natural compounds

Directory of Open Access Journals (Sweden)

Miroslav Palík

2014-09-01

Full Text Available The study of Pd-catalysed cyclisation reactions of alkenols using different catalytic systems is reported. These transformations affect the stereoselective construction of mono- and/or bicyclic oxaheterocyclic derivatives depending on a starting alkenol. The substrate scope and proposed mechanism of Pd-catalysed cyclisation reactions are also discussed. Moreover, the diastereoselective Pd-catalysed cyclisation of appropriate alkenols to tetrahydrofurans and subsequent cyclisation provided properly substituted 2,5-dioxabicyclo[2.2.1]heptane and 2,6-dioxabicyclo[3.2.1]octane, respectively. Such bicyclic ring subunits are found in many natural products including ocellenynes and aurovertines.

Molecular, phylogenetic and comparative genomic analysis of the cytokinin oxidase/dehydrogenase gene family in the Poaceae.

Science.gov (United States)

Mameaux, Sabine; Cockram, James; Thiel, Thomas; Steuernagel, Burkhard; Stein, Nils; Taudien, Stefan; Jack, Peter; Werner, Peter; Gray, John C; Greenland, Andy J; Powell, Wayne

2012-01-01

The genomes of cereals such as wheat (Triticum aestivum) and barley (Hordeum vulgare) are large and therefore problematic for the map-based cloning of agronomicaly important traits. However, comparative approaches within the Poaceae permit transfer of molecular knowledge between species, despite their divergence from a common ancestor sixty million years ago. The finding that null variants of the rice gene cytokinin oxidase/dehydrogenase 2 (OsCKX2) result in large yield increases provides an opportunity to explore whether similar gains could be achieved in other Poaceae members. Here, phylogenetic, molecular and comparative analyses of CKX families in the sequenced grass species rice, brachypodium, sorghum, maize and foxtail millet, as well as members identified from the transcriptomes/genomes of wheat and barley, are presented. Phylogenetic analyses define four Poaceae CKX clades. Comparative analyses showed that CKX phylogenetic groupings can largely be explained by a combination of local gene duplication, and the whole-genome duplication event that predates their speciation. Full-length OsCKX2 homologues in barley (HvCKX2.1, HvCKX2.2) and wheat (TaCKX2.3, TaCKX2.4, TaCKX2.5) are characterized, with comparative analysis at the DNA, protein and genetic/physical map levels suggesting that true CKX2 orthologs have been identified. Furthermore, our analysis shows CKX2 genes in barley and wheat have undergone a Triticeae-specific gene-duplication event. Finally, by identifying ten of the eleven CKX genes predicted to be present in barley by comparative analyses, we show that next-generation sequencing approaches can efficiently determine the gene space of large-genome crops. Together, this work provides the foundation for future functional investigation of CKX family members within the Poaceae. © 2011 National Institute of Agricultural Botany (NIAB). Plant Biotechnology Journal © 2011 Society for Experimental Biology, Association of Applied Biologists and Blackwell

Cytokinin Activity in Water-stressed Shoots 1

Science.gov (United States)

Itai, Chanan; Vaadia, Yoash

1971-01-01

Water stress applied to the plant shoot through enhanced evaporative demands reduced cytokinin activity in extracts of xylem exudate and leaves. This reduction resembled the changes in cytokinin activity caused by water stress applied to the root. Cytokinin activity in detached wilting leaves decreased rapidly. Recovery took place after several hours in a humid chamber. Experiments with 14C-kinetin indicated that the mechanism of the inactivation and its reversal involve a chemical transformation of the cytokinin molecule. PMID:16657585

Chlorodifluoromethane-triggered formation of difluoromethylated arenes catalysed by palladium

Science.gov (United States)

Feng, Zhang; Min, Qiao-Qiao; Fu, Xia-Ping; An, Lun; Zhang, Xingang

2017-09-01

Difluoromethylated aromatic compounds are of increasing importance in pharmaceuticals, agrochemicals and materials. Chlorodifluoromethane (ClCF2H), an inexpensive, abundant and widely used industrial raw material, represents the ideal and most straightforward difluoromethylating reagent, but introduction of the difluoromethyl group (CF2H) from ClCF2H into aromatics has not been reported. Here, we describe a direct palladium-catalysed difluoromethylation method for coupling ClCF2H with arylboronic acids and esters to generate difluoromethylated arenes with high efficiency. The reaction exhibits a remarkably broad substrate scope, including heteroarylboronic acids, and was used for difluoromethylation of a range of pharmaceuticals and biologically active compounds. Preliminary mechanistic studies revealed that a palladium difluorocarbene intermediate is involved in the reaction. Although numerous metal-difluorocarbene complexes have been prepared, the catalytic synthesis of difluoromethylated or difluoromethylenated compounds involving metal-difluorocarbene complexes has not received much attention. This new reaction therefore also opens the door to understand metal-difluorocarbene complex catalysed reactions.

Bifluoride-catalysed sulfur(VI) fluoride exchange reaction for the synthesis of polysulfates and polysulfonates

Science.gov (United States)

Gao, Bing; Zhang, Linda; Zheng, Qinheng; Zhou, Feng; Klivansky, Liana M.; Lu, Jianmei; Liu, Yi; Dong, Jiajia; Wu, Peng; Sharpless, K. Barry

2017-11-01

Polysulfates and polysulfonates possess exceptional mechanical properties making them potentially valuable engineering polymers. However, they have been little explored due to a lack of reliable synthetic access. Here we report bifluoride salts (Q+[FHF]-, where Q+ represents a wide range of cations) as powerful catalysts for the sulfur(VI) fluoride exchange (SuFEx) reaction between aryl silyl ethers and aryl fluorosulfates (or alkyl sulfonyl fluorides). The bifluoride salts are significantly more active in catalysing the SuFEx reaction compared to organosuperbases, therefore enabling much lower catalyst-loading (down to 0.05 mol%). Using this chemistry, we are able to prepare polysulfates and polysulfonates with high molecular weight, narrow polydispersity and excellent functional group tolerance. The process is practical with regard to the reduced cost of catalyst, polymer purification and by-product recycling. We have also observed that the process is not sensitive to scale-up, which is essential for its future translation from laboratory research to industrial applications.

Iron-catalysed fluoroaromatic coupling reactions under catalytic modulation with 1,2-bis(diphenylphosphino)benzene.

Science.gov (United States)

Hatakeyama, Takuji; Kondo, Yoshiyuki; Fujiwara, Yu-Ichi; Takaya, Hikaru; Ito, Shingo; Nakamura, Eiichi; Nakamura, Masaharu

2009-03-14

A catalytic amount of 1,2-bis(diphenylphosphino)benzene (DPPBz) achieves selective cleavage of sp(3)-carbon-halogen bond in the iron-catalysed cross-coupling between polyfluorinated arylzinc reagents and alkyl halides, which was unachievable with a stoichiometric modifier such as TMEDA; the selective iron-catalysed fluoroaromatic coupling provides easy and practical access to polyfluorinated aromatic compounds.

Glucose and Fructose to Platform Chemicals: Understanding the Thermodynamic Landscapes of Acid-Catalysed Reactions Using High-Level ab Initio Methods

Energy Technology Data Exchange (ETDEWEB)

Assary, Rajeev S.; Kim, Taijin; Low, John; Greeley, Jeffrey P.; Curtiss, Larry A.

2012-12-28

Molecular level understanding of acid-catalysed conversion of sugar molecules to platform chemicals such as hydroxy-methyl furfural (HMF), furfuryl alcohol (FAL), and levulinic acid (LA) is essential for efficient biomass conversion. In this paper, the high-level G4MP2 method along with the SMD solvation model is employed to understand detailed reaction energetics of the acid-catalysed decomposition of glucose and fructose to HMF. Based on protonation free energies of various hydroxyl groups of the sugar molecule, the relative reactivity of gluco-pyranose, fructo-pyranose and fructo-furanose are predicted. Calculations suggest that, in addition to the protonated intermediates, a solvent assisted dehydration of one of the fructo-furanosyl intermediates is a competing mechanism, indicating the possibility of multiple reaction pathways for fructose to HMF conversion in aqueous acidic medium. Two reaction pathways were explored to understand the thermodynamics of glucose to HMF; the first one is initiated by the protonation of a C2–OH group and the second one through an enolate intermediate involving acyclic intermediates. Additionally, a pathway is proposed for the formation of furfuryl alcohol from glucose initiated by the protonation of a C2–OH position, which includes a C–C bond cleavage, and the formation of formic acid. The detailed free energy landscapes predicted in this study can be used as benchmarks for further exploring the sugar decomposition reactions, prediction of possible intermediates, and finally designing improved catalysts for biomass conversion chemistry in the future.

Proteome and metabolome profiling of cytokinin action in Arabidopsis identifying both distinct and similar responses to cytokinin down- and up-regulation.

Science.gov (United States)

Černý, Martin; Kuklová, Alena; Hoehenwarter, Wolfgang; Fragner, Lena; Novák, Ondrej; Rotková, Gabriela; Jedelsky, Petr L; Žáková, Katerina; Šmehilová, Mária; Strnad, Miroslav; Weckwerth, Wolfram; Brzobohaty, Bretislav

2013-11-01

In plants, numerous developmental processes are controlled by cytokinin (CK) levels and their ratios to levels of other hormones. While molecular mechanisms underlying the regulatory roles of CKs have been intensely researched, proteomic and metabolomic responses to CK deficiency are unknown. Transgenic Arabidopsis seedlings carrying inducible barley cytokinin oxidase/dehydrogenase (CaMV35S>GR>HvCKX2) and agrobacterial isopentenyl transferase (CaMV35S>GR>ipt) constructs were profiled to elucidate proteome- and metabolome-wide responses to down- and up-regulation of CK levels, respectively. Proteome profiling identified >1100 proteins, 155 of which responded to HvCKX2 and/or ipt activation, mostly involved in growth, development, and/or hormone and light signalling. The metabolome profiling covered 79 metabolites, 33 of which responded to HvCKX2 and/or ipt activation, mostly amino acids, carbohydrates, and organic acids. Comparison of the data sets obtained from activated CaMV35S>GR>HvCKX2 and CaMV35S>GR>ipt plants revealed unexpectedly extensive overlaps. Integration of the proteomic and metabolomic data sets revealed: (i) novel components of molecular circuits involved in CK action (e.g. ribosomal proteins); (ii) previously unrecognized links to redox regulation and stress hormone signalling networks; and (iii) CK content markers. The striking overlaps in profiles observed in CK-deficient and CK-overproducing seedlings might explain surprising previously reported similarities between plants with down- and up-regulated CK levels.

Hydrogen storage and evolution catalysed by metal hydride complexes.

Science.gov (United States)

Fukuzumi, Shunichi; Suenobu, Tomoyoshi

2013-01-07

The storage and evolution of hydrogen are catalysed by appropriate metal hydride complexes. Hydrogenation of carbon dioxide by hydrogen is catalysed by a [C,N] cyclometalated organoiridium complex, [Ir(III)(Cp*)(4-(1H-pyrazol-1-yl-κN(2))benzoic acid-κC(3))(OH(2))](2)SO(4) [Ir-OH(2)](2)SO(4), under atmospheric pressure of H(2) and CO(2) in weakly basic water (pH 7.5) at room temperature. The reverse reaction, i.e., hydrogen evolution from formate, is also catalysed by [Ir-OH(2)](+) in acidic water (pH 2.8) at room temperature. Thus, interconversion between hydrogen and formic acid in water at ambient temperature and pressure has been achieved by using [Ir-OH(2)](+) as an efficient catalyst in both directions depending on pH. The Ir complex [Ir-OH(2)](+) also catalyses regioselective hydrogenation of the oxidised form of β-nicotinamide adenine dinucleotide (NAD(+)) to produce the 1,4-reduced form (NADH) under atmospheric pressure of H(2) at room temperature in weakly basic water. In weakly acidic water, the complex [Ir-OH(2)](+) also catalyses the reverse reaction, i.e., hydrogen evolution from NADH to produce NAD(+) at room temperature. Thus, interconversion between NADH (and H(+)) and NAD(+) (and H(2)) has also been achieved by using [Ir-OH(2)](+) as an efficient catalyst and by changing pH. The iridium hydride complex formed by the reduction of [Ir-OH(2)](+) by H(2) and NADH is responsible for the hydrogen evolution. Photoirradiation (λ > 330 nm) of an aqueous solution of the Ir-hydride complex produced by the reduction of [Ir-OH(2)](+) with alcohols resulted in the quantitative conversion to a unique [C,C] cyclometalated Ir-hydride complex, which can catalyse hydrogen evolution from alcohols in a basic aqueous solution (pH 11.9). The catalytic mechanisms of the hydrogen storage and evolution are discussed by focusing on the reactivity of Ir-hydride complexes.

Combined high-performance liquid chromatography-radioimmunoassay for cytokinins

International Nuclear Information System (INIS)

MacDonald, E.M.S.; Akiyoshi, D.E.; Morris, R.O.

1981-01-01

The cytokinins isopentenyladenosine and ribosylzeatin were conjugated to bovine serum albumin and the conjugates used to raise antisera in rabbits. The resulting antisera had high specificity towards the cytokinin haptens and low cross-reactivity towards other purines. They were used as the basis for a radioimmunoassay for cytokinins, which, when applied in conjunction with high-performance liquid chromatography, allowed rapid and sensitive (to the picogram range) estimation and identification of multiple cytokinins from natural plant and bacterial sources. (orig.)

Changes in cytokinin levels and metabolism in tobacco (Nicotiana tabacum L.) explants during in vitro shoot organogenesis induced by trans-zeatin and dihydrozeatin

Czech Academy of Sciences Publication Activity Database

Klemš, M.; Slámová, Z.; Motyka, Václav; Malbeck, Jiří; Trávníčková, Alena; Macháčková, Ivana; Holík, Josef; Procházka, S.

2011-01-01

Roč. 65, č. 3 (2011), s. 427-437 ISSN 0167-6903 R&D Projects: GA MŠk 1M06030; GA ČR(CZ) GAP506/11/0774; GA AV ČR IAA600380701 Institutional research plan: CEZ:AV0Z50380511 Keywords : Beta-glucosidase * Cytokinin oxidase/ dehydrogenase * Dihydrozeatin Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 1.604, year: 2011

Cytokinins, A classical multifaceted hormone in plant system

Directory of Open Access Journals (Sweden)

Mohd Mazid

2011-12-01

Full Text Available Today, owing to the versatile functionality and physiological importance of the phytohormone cytokinin (Ck is a major focus of attention in contemporary wide areas of plant science. Cytokinins (Cks have implicated in diverse essential processes of plant growth and development as well as in regulation of key genes responsible for the metabolism and activities of plants. Cytokinin interact in a complex manner to control a myriad of aspects related to growth, development and differentiation and its deficiency also causes pleiotropic developmental changes such as reduced shoot and increased root growth. Cytokinin signaling involves His Kinase receptors that perceive cytokinin and transmit the signal via a multi-step phosphorelay similar to bacterial two-component signaling system. Also, this review present a scheme for homeostatic regulation of endogenous cytokinins level in terms of the described mechanism of cytokinin action including its receptors and steps involved in regulation of gene expression at the post-transcriptional level and its role in whole plant as well as cell division. In addition, we also demonstrate a wide variety of biological effects including those on gene expression, inhibition of auxin action, stimulation of cell cycle etc.

ENDOGENOUS CYTOKININS IN MEDICINAL BASIDIOMYCETES MYCELIAL BIOMASS

Directory of Open Access Journals (Sweden)

N. P.

2016-02-01

Full Text Available The aim of the research was to study the cytokinins production by medicinal basidial mushrooms. Cytokinins were for the first time identified and quantified in mycelial biomass of six species (Ganoderma lucidum, Trametes versicolor, Fomitopsis officinalis, Pleurotus nebrodensis, Grifola frondosa, Sparassis crispa using HPLC. Trans- and cis-zeatin, zeatin riboside, zeatin-O-glucoside, isopentenyladenosine, isopentenyladenine were found but only one species (G. lucidum, strain 1900 contained all these substances. The greatest total cytokinin quantity was detected in F. officinalis, strain 5004. S. crispa, strain 314, and F. officinalis, strain 5004, mycelial biomass was revealed to have the highest level of cytokinin riboside forms (zeatin riboside and isopentenyladenosine. The possible connection between medicinal properties of investigated basidiomycetes and of cytokinins is discussed. S. crispa, strain 314, and F. officinalis, strain 5004, are regarded as promising species for developing biotechnological techniques to produce biologically active drugs from their mycelial biomass. As one of the potential technological approaches there is proposed fungal material drying.

Light influences cytokinin biosynthesis and sensing in Nostoc (cyanobacteria).

Science.gov (United States)

Frébortová, Jitka; Plíhal, Ondřej; Florová, Vendula; Kokáš, Filip; Kubiasová, Karolina; Greplová, Marta; Šimura, Jan; Novák, Ondřej; Frébort, Ivo

2017-06-01

Cytokinins are an important group of plant hormones that are also found in other organisms, including cyanobacteria. While various aspects of cytokinin function and metabolism are well understood in plants, the information is limited for cyanobacteria. In this study, we first experimentally confirmed a prenylation of tRNA by recombinant isopentenyl transferase NoIPT2 from Nostoc sp. PCC 7120, whose encoding gene we previously identified in Nostoc genome along with the gene for adenylate isopentenyl transferase NoIPT1. In contrast to NoIPT2, the transcription of NoIPT1 was strongly activated during the dark period and was followed by an increase in the cytokinin content several hours later in the light period. Dominant cytokinin metabolites detected at all time points were free bases and monophosphates of isopentenyladenine and cis-zeatin, while N-glucosides were not detected at all. Whole transcriptome differential expression analysis of cultures of the above Nostoc strain treated by cytokinin compared to untreated controls indicated that cytokinin together with light trigger expression of several genes related to signal transduction, including two-component sensor histidine kinases and two-component hybrid sensors and regulators. One of the affected histidine kinases with a cyclase/histidine kinase-associated sensory extracellular domain similar to the cytokinin-binding domain in plant cytokinin receptors was able to modestly bind isopentenyladenine. The data show that the genetic disposition allows Nostoc not only to produce free cytokinins and prenylate tRNA but also modulate the cytokinin biosynthesis in response to light, triggering complex changes in sensing and regulation. © 2017 Phycological Society of America.

catalysed ortho-carboxylation of acetanilide with CO

Indian Academy of Sciences (India)

Abstract. The mechanism of palladium(II)-catalysed carboxylation of acetanilide with CO has been investi- gated using density functional theory calculation done at the B3LYP/6-31G(d, p)(SDD for Pd) level of theory. Solvent effects on these reactions have been explored by calculation that included a polarizable continuum.

A new strategy to inhibit the excision reaction catalysed by HIV-1 reverse transcriptase: compounds that compete with the template–primer

Science.gov (United States)

Cruchaga, Carlos; Anso, Elena; Font, María; Martino, Virginia S.; Rouzaut, Ana; Martinez-Irujo, Juan J.

2007-01-01

Inhibitors of the excision reaction catalysed by HIV-1 RT (reverse transcriptase) represent a promising approach in the fight against HIV, because these molecules would interfere with the main mechanism of resistance of this enzyme towards chain-terminating nucleotides. Only a limited number of compounds have been demonstrated to inhibit this reaction to date, including NNRTIs (non-nucleoside RT inhibitors) and certain pyrophosphate analogues. We have found previously that 2GP (2-O-galloylpunicalin), an antiviral compound extracted from the leaves of Terminalia triflora, was able to inhibit both the RT and the RNase H activities of HIV-1 RT without affecting cell proliferation or viability. In the present study, we show that 2GP also inhibited the ATP- and PPi-dependent phosphorolysis catalysed by wild-type and AZT (3′-azido-3′-deoxythymidine)-resistant enzymes at sub-micromolar concentrations. Kinetic and direct-binding analysis showed that 2GP was a non-competitive inhibitor against the nucleotide substrate, whereas it competed with the binding of RT to the template–primer (Kd=85 nM). As expected from its mechanism of action, 2GP was active against mutations conferring resistance to NNRTIs and AZT. The combination of AZT with 2GP was highly synergistic when tested in the presence of pyrophosphate, indicating that the inhibition of RT-catalysed phosphorolysis was responsible for the synergy found. Although other RT inhibitors that compete with the template–primer have been described, this is the first demonstration that these compounds can be used to block the excision of chain terminating nucleotides, providing a rationale for their combination with nucleoside analogues. PMID:17355225

Cytokinin oxidase/dehydrogenase overexpression modifies antioxidant defense against heat, drought and their combination in Nicotiana tabacum plants

Czech Academy of Sciences Publication Activity Database

Lubovská, Zuzana; Dobrá, Jana; Štorchová, Helena; Wilhelmová, Naděžda; Vaňková, Radomíra

2014-01-01

Roč. 171, č. 17 (2014), s. 1625-1633 ISSN 0176-1617 R&D Projects: GA ČR GA206/09/2062; GA MŠk LD14120 Institutional support: RVO:61389030 Keywords : Antioxidant enzymes * Cytokinin * Drought Subject RIV: ED - Physiology Impact factor: 2.557, year: 2014 http://gateway.isiknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcAuth=Alerting&SrcApp=Alerting&DestApp=MEDLINE&DestLinkType=FullRecord&UT=25171514

Cytokinin signaling during root development.

Science.gov (United States)

Bishopp, Anthony; Help, Hanna; Helariutta, Ykä

2009-01-01

The cytokinin class of phytohormones regulates division and differentiation of plant cells. They are perceived and signaled by a phosphorelay mechanism similar to those observed in prokaryotes. Research into the components of phosphorelay had previously been marred by genetic redundancy. However, recent studies have addressed this with the creation of high-order mutants. In addition, several new elements regulating cytokinin signaling have been identified. This has uncovered many roles in diverse developmental and physiological processes. In this review, we look at these processes specifically in the context of root development. We focus on the formation and maintenance of the root apical meristem, primary and secondary vascular development, lateral root emergence and development, and root nodulation. We believe that the root is an ideal organ with which to investigate cytokinin signaling in a wider context.

Characterisation of hydrocarbonaceous overlayers important in metal-catalysed selective hydrogenation reactions

Energy Technology Data Exchange (ETDEWEB)

Lennon, David; Warringham, Robbie [School of Chemistry, Joseph Black Building, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Guidi, Tatiana [ISIS Facility, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX (United Kingdom); Parker, Stewart F., E-mail: stewart.parker@stfc.ac.uk [ISIS Facility, STFC Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX (United Kingdom)

2013-12-12

Highlights: • Inelastic neutron scattering spectroscopy of a commercial dehydrogenation catalyst. • The overlayer present on the catalyst is predominantly aliphatic. • A population of strongly hydrogen bonded hydroxyls is also present. - Abstract: The hydrogenation of alkynes to alkenes over supported metal catalysts is an important industrial process and it has been shown that hydrocarbonaceous overlayers are important in controlling selectivity profiles of metal-catalysed hydrogenation reactions. As a model system, we have selected propyne hydrogenation over a commercial Pd(5%)/Al{sub 2}O{sub 3} catalyst. Inelastic neutron scattering studies show that the C–H stretching mode ranges from 2850 to 3063 cm{sup −1}, indicating the mostly aliphatic nature of the overlayer and this is supported by the quantification of the carbon and hydrogen on the surface. There is also a population of strongly hydrogen-bonded hydroxyls, their presence would indicate that the overlayer probably contains some oxygen functionality. There is little evidence for any olefinic or aromatic species. This is distinctly different from the hydrogen-poor overlayers that are deposited on Ni/Al{sub 2}O{sub 3} catalysts during methane reforming.

Use of cytokinins as agrochemicals.

Science.gov (United States)

Koprna, Radoslav; De Diego, Nuria; Dundálková, Lucie; Spíchal, Lukáš

2016-02-01

Plant hormones cytokinins regulate various aspects of plant growth and development. For their positive effects on branching, delaying of senescence, nutrient remobilisation, flower and seed set control they became interesting substances in search for potential agrochemicals. From the 1970' of the last century exogenous application of cytokinins have been tested in field conditions to improve yield traits of world-wide important crops such as wheat, rice, maize, barley, and soybean. Despite the extensive testing summarized in this work, so far cytokinins haven't found their stable place among commercialized plant growth regulators, mainly due to the complexity of their effects. Here we bring an overview of the outcomes obtained in pot and field experiments using cytokinin exogenous treatments, summarize the ways of application and point to the affected traits in various field crops, vegetables, cotton and fruit trees. Further, we present here outcomes of field trials performed with a derivative of N(6)-benzyladenine, 2-chloro-6-(3-methoxybenzyl)aminopurine, in spring barley and winter wheat. The effect on yield forming traits such as number of tillers, grains per ear, number of ears and the final yield was evaluated and compared after spraying of the both crops in different phenological stages. Copyright © 2015 Elsevier Ltd. All rights reserved.

Alginate as immobilization matrix and stabilizing agent in a two-phase liquid system: application in lipase-catalysed reactions.

Science.gov (United States)

Hertzberg, S; Kvittingen, L; Anthonsen, T; Skjåk-Braek, G

1992-01-01

Alginate was evaluated as an immobilization matrix for enzyme-catalyzed reactions in organic solvents. In contrast to most hydrogels, calcium alginate was found to be stable in a range of organic solvents and to retain the enzyme inside the gel matrix. In hydrophobic solvents, the alginate gel (greater than 95% water) thus provided a stable, two-phase liquid system. The lipase from Candida cylindracea, after immobilization in alginate beads, catalysed esterification and transesterification in n-hexane under both batch and continuous-flow conditions. The operational stability of the lipase was markedly enhanced by alginate entrapment. In the esterification of butanoic acid with n-butanol, better results were obtained in the typical hydrophilic calcium alginate beads than in less hydrophilic matrices. The effects of substrate concentration, matrix area, and polarity of the substrate alcohols and of the organic solvent on the esterification activity were examined. The transesterification of octyl 2-bromopropanoate with ethanol was less efficient than that of ethyl 2-bromopropanoate with octanol. By using the hydrophilic alginate gel as an immobilization matrix in combination with a mobile hydrophobic phase, a two-phase liquid system was achieved with definite advantages for a continuous, enzyme-catalysed process.

Trans-Selective Rhodium Catalysed Conjugate Addition of Organoboron Reagents to Dihydropyranones

Directory of Open Access Journals (Sweden)

Hannah J. Edwards

2015-04-01

Full Text Available The selective synthesis of 2,6-trans-tetrahydropyran derivatives employing the rhodium catalysed addition of organoboron reagents to dihydropyranone templates, derived from a zinc-catalysed hetero-Diels-Alder reaction, is reported. The addition of both arylboronic acids and potassium alkenyltrifluoroborates have been accomplished in high yields using commercially-available [Rh(cod(OH]2 catalyst. The selective formation of the 2,6-trans-tetrahydropyran stereoisomer is consistent with a mechanism involving alkene association and carbometalation on the less hindered face of the dihydropyranone.

Systems biology and the origins of life? part II. Are biochemical networks possible ancestors of living systems? networks of catalysed chemical reactions: non-equilibrium, self-organization and evolution.

Science.gov (United States)

Ricard, Jacques

2010-01-01

The present article discusses the possibility that catalysed chemical networks can evolve. Even simple enzyme-catalysed chemical reactions can display this property. The example studied is that of a two-substrate proteinoid, or enzyme, reaction displaying random binding of its substrates A and B. The fundamental property of such a system is to display either emergence or integration depending on the respective values of the probabilities that the enzyme has bound one of its substrate regardless it has bound the other substrate, or, specifically, after it has bound the other substrate. There is emergence of information if p(A)>p(AB) and p(B)>p(BA). Conversely, if p(A)equilibrium. Moreover, in such systems, emergence results in an increase of the energy level of the ternary EAB complex that becomes closer to the transition state of the reaction, thus leading to the enhancement of catalysis. Hence a drift from quasi-equilibrium is, to a large extent, responsible for the production of information and enhancement of catalysis. Non-equilibrium of these simple systems must be an important aspect that leads to both self-organization and evolutionary processes. These conclusions can be extended to networks of catalysed chemical reactions. Such networks are, in fact, networks of networks, viz. meta-networks. In this formal representation, nodes are chemical reactions catalysed by poorly specific proteinoids, and links can be identified to the transport of metabolites from proteinoid to proteinoid. The concepts of integration and emergence can be applied to such situations and can be used to define the identity of these networks and therefore their evolution. Defined as open non-equilibrium structures, such biochemical networks possess two remarkable properties: (1) the probability of occurrence of their nodes is dependant upon the input and output of matter in, and from, the system and (2) the probability of occurrence of the nodes is strictly linked to their degree of

The influence of oscillations on product selectivity during the palladium-catalysed phenylacetylene oxidative carbonylation reaction.

Science.gov (United States)

Novakovic, Katarina; Grosjean, Christophe; Scott, Stephen K; Whiting, Andrew; Willis, Mark J; Wright, Allen R

2008-02-07

This paper reports on the influence of oscillations on product selectivity as well as the dynamics of product formation during the palladium-catalysed phenylacetylene oxidative carbonylation reaction in a catalytic system (PdI2, KI, Air, NaOAc in methanol). The occurrence of the pH oscillations is related to PdI2 granularity and the initial pH drop after phenylacetylene addition. To achieve pH and reaction exotherm oscillations regulation of the amount of PdI2 is required, ensuring that the initial pH does not fall significantly below 1 after phenylacetylene addition. Experiments in both oscillatory and non-oscillatory pH regimes were performed in an HEL SIMULAR reaction calorimeter with the concentration-time profiles measured using a GC-MS. It is demonstrated that when operating in an oscillatory pH regime product formation may be suppressed until oscillations occur after which there is a steep increase in the formation of Z-2-phenyl-but-2-enedioic acid dimethyl ester. When operating in non-oscillatory pH mode the products are formed steadily over time with the main products being Z-2-phenyl-but-2-enedioic acid dimethyl ester, 2-phenyl-acrylic acid methyl ester and E-3-phenyl-acrylic acid methyl ester.

Overexpression of the WOX gene STENOFOLIA improves biomass yield and sugar release in transgenic grasses and display altered cytokinin homeostasis.

Directory of Open Access Journals (Sweden)

Hui Wang

2017-03-01

Full Text Available Lignocellulosic biomass can be a significant source of renewable clean energy with continued improvement in biomass yield and bioconversion strategies. In higher plants, the leaf blade is the central energy convertor where solar energy and CO2 are assimilated to make the building blocks for biomass production. Here we report that introducing the leaf blade development regulator STENOFOLIA (STF, a WOX family transcription factor, into the biofuel crop switchgrass, significantly improves both biomass yield and sugar release. We found that STF overexpressing switchgrass plants produced approximately 2-fold more dry biomass and release approximately 1.8-fold more solubilized sugars without pretreatment compared to controls. The biomass increase was attributed mainly to increased leaf width and stem thickness, which was also consistent in STF transgenic rice and Brachypodium, and appeared to be caused by enhanced cell proliferation. STF directly binds to multiple regions in the promoters of some cytokinin oxidase/dehydrogenase (CKX genes and represses their expression in all three transgenic grasses. This repression was accompanied by a significant increase in active cytokinin content in transgenic rice leaves, suggesting that the increase in biomass productivity and sugar release could at least in part be associated with improved cytokinin levels caused by repression of cytokinin degrading enzymes. Our study provides a new tool for improving biomass feedstock yield in bioenergy crops, and uncovers a novel mechanistic insight in the function of STF, which may also apply to other repressive WOX genes that are master regulators of several key plant developmental programs.

Phenylboronic acid catalysed synthesis of 1,5-benzodiazepines via ...

Indian Academy of Sciences (India)

J. Chem. Sci. Vol. 125, No. 4, July 2013, pp. 745–749. c Indian Academy of Sciences. Phenylboronic acid catalysed synthesis of 1,5-benzodiazepines via cyclocondensation of ... active compounds and gaining great consideration in the field of .... thesis of this heterocycles was accomplished by con- densation reaction of ...

Determination of glutamate dehydrogenase activity and its kinetics in mouse tissues using metabolic mapping (quantitative enzyme histochemistry)

NARCIS (Netherlands)

Botman, Dennis; Tigchelaar, Wikky; van Noorden, Cornelis J. F.

2014-01-01

Glutamate dehydrogenase (GDH) catalyses the reversible conversion of glutamate into α-ketoglutarate with the concomitant reduction of NAD(P)(+) to NAD(P)H or vice versa. GDH activity is subject to complex allosteric regulation including substrate inhibition. To determine GDH kinetics in situ, we

Analysis of 2-methylthio-derivatives of isoprenoid cytokinins by liquid chromatography-tandem mass spectrometry

Energy Technology Data Exchange (ETDEWEB)

Tarkowski, Petr, E-mail: petr.tarkowski@upol.cz [Laboratory of Growth Regulators, Palacky University and Institute of Experimental Botany ASCR, Slechtitelu 11, 783 71 Olomouc (Czech Republic); Department of Biochemistry, Faculty of Science, Palacky University, Slechtitelu 11, 783 71 Olomouc (Czech Republic); Vaclavikova, Katerina, E-mail: katka.vaclavik@seznam.cz [Laboratory of Growth Regulators, Palacky University and Institute of Experimental Botany ASCR, Slechtitelu 11, 783 71 Olomouc (Czech Republic); Department of Biochemistry, Faculty of Science, Palacky University, Slechtitelu 11, 783 71 Olomouc (Czech Republic); Novak, Ondrej, E-mail: ondrej.novak@upol.cz [Laboratory of Growth Regulators, Palacky University and Institute of Experimental Botany ASCR, Slechtitelu 11, 783 71 Olomouc (Czech Republic); Pertry, Ine, E-mail: ine.pertry@ugent.BE [Department of Plant Biotechnology and Genetics, Ghent University, K.L.Ledeganckstraat 35, B-9000 Gent (Belgium); Hanus, Jan, E-mail: helehan@seznam.cz [Isotope Laboratory, Institute of Experimental Botany ASCR, Videnska 1083, 142 20 Prague (Czech Republic); Whenham, Robert [Apex Organics, Devon, England (United Kingdom); Vereecke, Danny, E-mail: danny.vereecke@hogent.BE [Department of Plant Production, University College Ghent, Ghent University, Schoonmeersstraat 52, B-9000 Gent (Belgium); Sebela, Marek, E-mail: marek.sebela@upol.cz [Department of Biochemistry, Faculty of Science, Palacky University, Slechtitelu 11, 783 71 Olomouc (Czech Republic); Strnad, Miroslav, E-mail: miroslav.strnad@upol.cz [Laboratory of Growth Regulators, Palacky University and Institute of Experimental Botany ASCR, Slechtitelu 11, 783 71 Olomouc (Czech Republic)

2010-11-08

A sensitive and reliable high-performance liquid chromatographic method with tandem mass spectrometric detection has been developed and used for the determination of 2-methylthio-cytokinin derivatives produced by the phytopathogenic actinomycete Rhodococcus fascians. The cultivation medium containing secreted cytokinins was concentrated and subjected to a solid-phase extraction (C18 and ion-exchange). The purified samples were further separated and analyzed by HPLC-ESI-MS/MS. This allowed to achieve chromatographic resolution of six highly hydrophobic cytokinin species including 2-methylthio-isopentenyladenine, 2-methylthio-isopentenyladenosine, 2-methylthio-trans-zeatin and 2-methylthio-trans-zeatin riboside and their cis-isomers when a reversed-phase chromatographic column (C4) and a mobile phase consisting of acetonitrile and 20 mM ammonium formate, pH 5, were used. Quantification was performed by a standard isotope dilution method using a multiple-reaction monitoring (MRM) mode. In the MRM mode, limits of detection reached 20-30 fmol and linear ranges spanned four orders of magnitude. Recovery values were between 35% and 65% and the analytical accuracy between 95% and 149%. The proposed bioanalytical method, which takes advantage of effective chromatographic separation of six 2-methyltio-derivatives (including isomers of zeatin-type cytokinins) and sensitive mass spectrometric detection, may become useful for plant biologists studying the significance of these substances in plant-microbe interactions.

Analysis of 2-methylthio-derivatives of isoprenoid cytokinins by liquid chromatography-tandem mass spectrometry

International Nuclear Information System (INIS)

Tarkowski, Petr; Vaclavikova, Katerina; Novak, Ondrej; Pertry, Ine; Hanus, Jan; Whenham, Robert; Vereecke, Danny; Sebela, Marek; Strnad, Miroslav

2010-01-01

A sensitive and reliable high-performance liquid chromatographic method with tandem mass spectrometric detection has been developed and used for the determination of 2-methylthio-cytokinin derivatives produced by the phytopathogenic actinomycete Rhodococcus fascians. The cultivation medium containing secreted cytokinins was concentrated and subjected to a solid-phase extraction (C18 and ion-exchange). The purified samples were further separated and analyzed by HPLC-ESI-MS/MS. This allowed to achieve chromatographic resolution of six highly hydrophobic cytokinin species including 2-methylthio-isopentenyladenine, 2-methylthio-isopentenyladenosine, 2-methylthio-trans-zeatin and 2-methylthio-trans-zeatin riboside and their cis-isomers when a reversed-phase chromatographic column (C4) and a mobile phase consisting of acetonitrile and 20 mM ammonium formate, pH 5, were used. Quantification was performed by a standard isotope dilution method using a multiple-reaction monitoring (MRM) mode. In the MRM mode, limits of detection reached 20-30 fmol and linear ranges spanned four orders of magnitude. Recovery values were between 35% and 65% and the analytical accuracy between 95% and 149%. The proposed bioanalytical method, which takes advantage of effective chromatographic separation of six 2-methyltio-derivatives (including isomers of zeatin-type cytokinins) and sensitive mass spectrometric detection, may become useful for plant biologists studying the significance of these substances in plant-microbe interactions.

"On-water" rhodium-catalysed hydroformylation for the production of linear alcohols

NARCIS (Netherlands)

Diebolt, O.H.; Müller, Christian; Vogt, D.

2012-01-01

Optimisation of the reaction conditions for the rhodium-catalysed aldehyde hydrogenation under hydroformylation conditions showed that water used as co-solvent enhances both rate and selectivity towards primary alcohols. One-pot hydroformylation–hydrogenation using rhodium as the only transition

Stabilizing Effects of Deep Eutectic Solvents on Alcohol Dehydrogenase Mediated Systems

OpenAIRE

Fatima Zohra Ibn Majdoub Hassani; Ivan Lavandera; Joseph Kreit

2016-01-01

This study explored the effects of different organic solvents, temperature, and the amount of glycerol on the alcohol dehydrogenase (ADH)-catalysed stereoselective reduction of different ketones. These conversions were then analyzed by gas chromatography. It was found that when the amount of deep eutectic solvents (DES) increases, it can improve the stereoselectivity of the enzyme although reducing its ability to convert the substrate into the corresponding alcohol. Moreover, glycerol was fou...

Genetically engineered yeast

DEFF Research Database (Denmark)

2014-01-01

A genetically modified Saccharomyces cerevisiae comprising an active fermentation pathway producing 3-HP expresses an exogenous gene expressing the aminotransferase YhxA from Bacillus cereus AH1272 catalysing a transamination reaction between beta-alanine and pyruvate to produce malonate semialde......A genetically modified Saccharomyces cerevisiae comprising an active fermentation pathway producing 3-HP expresses an exogenous gene expressing the aminotransferase YhxA from Bacillus cereus AH1272 catalysing a transamination reaction between beta-alanine and pyruvate to produce malonate...... semialdehyde. The yeast may also express a 3-hydroxyisobutyrate dehydrogenase (HIBADH) and a 3-hydroxypropanoate dehydrogenase (3-HPDH) and aspartate 1-decarboxylase. Additionally the yeast may express pyruvate carboxylase and aspartate aminotransferase....

Cytokinin profiles in the conifer tree Abies nordmanniana

DEFF Research Database (Denmark)

Rasmussen, Hanne Nina; Veierskov, Bjarke; Hansen-Møller, Jens

2009-01-01

in the crown and root system were sampled destructively in 4- and 6-year-old trees and analyzed for a range of cytokinins by LC-MS/MS. No seasonal patterns were detected in the root samples, and a major portion of cytokinin was in conjugated forms. Dramatic and consistent seasonal changes occurred in the crown......Abstract  Conifer trees are routinely manipulated hormonally to increase flowering, branching, or adjust crown shape for production purposes. This survey of internal cytokinin levels provides a background for such treatments in Abies nordmanniana, a tree of great economic interest. Reference points...

Identification and expression analysis of cytokinin metabolic genes IPTs, CYP735A and CKXs in the biofuel plant Jatropha curcas

Science.gov (United States)

Cai, Li; Zhang, Lu

2018-01-01

The seed oil of Jatropha curcas is considered a potential bioenergy source that could replace fossil fuels. However, the seed yield of Jatropha is low and has yet to be improved. We previously reported that exogenous cytokinin treatment increased the seed yield of Jatropha. Cytokinin levels are directly regulated by isopentenyl transferase (IPT), cytochrome P450 monooxygenase, family 735, subfamily A (CYP735A), and cytokinin oxidase/dehydrogenase (CKX). In this study, we cloned six IPT genes, one JcCYP735A gene, and seven JcCKX genes. The expression patterns of these 14 genes in various organs were determined using real-time quantitative PCR. JcIPT1 was primarily expressed in roots and seeds, JcIPT2 was expressed in roots, apical meristems, and mature leaves, JcIPT3 was expressed in stems and mature leaves, JcIPT5 was expressed in roots and mature leaves, JcIPT6 was expressed in seeds at 10 days after pollination, and JcIPT9 was expressed in mature leaves. JcCYP735A was mainly expressed in roots, flower buds, and seeds. The seven JcCKX genes also showed different expression patterns in different organs of Jatropha. In addition, CK levels were detected in flower buds and seeds at different stages of development. The concentration of N6-(Δ2-isopentenyl)-adenine (iP), iP-riboside, and trans-zeatin (tZ) increased with flower development, and the concentration of iP decreased with seed development, while that of tZ increased. We further analyzed the function of JcCYP735A using the CRISPR-Cas9 system, and found that the concentrations of tZ and tZ-riboside decreased significantly in the Jccyp735a mutants, which showed severely retarded growth. These findings will be helpful for further studies of the functions of cytokinin metabolic genes and understanding the roles of cytokinins in Jatropha growth and development. PMID:29785355

Identification and expression analysis of cytokinin metabolic genes IPTs, CYP735A and CKXs in the biofuel plant Jatropha curcas

Directory of Open Access Journals (Sweden)

Li Cai

2018-05-01

Full Text Available The seed oil of Jatropha curcas is considered a potential bioenergy source that could replace fossil fuels. However, the seed yield of Jatropha is low and has yet to be improved. We previously reported that exogenous cytokinin treatment increased the seed yield of Jatropha. Cytokinin levels are directly regulated by isopentenyl transferase (IPT, cytochrome P450 monooxygenase, family 735, subfamily A (CYP735A, and cytokinin oxidase/dehydrogenase (CKX. In this study, we cloned six IPT genes, one JcCYP735A gene, and seven JcCKX genes. The expression patterns of these 14 genes in various organs were determined using real-time quantitative PCR. JcIPT1 was primarily expressed in roots and seeds, JcIPT2 was expressed in roots, apical meristems, and mature leaves, JcIPT3 was expressed in stems and mature leaves, JcIPT5 was expressed in roots and mature leaves, JcIPT6 was expressed in seeds at 10 days after pollination, and JcIPT9 was expressed in mature leaves. JcCYP735A was mainly expressed in roots, flower buds, and seeds. The seven JcCKX genes also showed different expression patterns in different organs of Jatropha. In addition, CK levels were detected in flower buds and seeds at different stages of development. The concentration of N6-(Δ2-isopentenyl-adenine (iP, iP-riboside, and trans-zeatin (tZ increased with flower development, and the concentration of iP decreased with seed development, while that of tZ increased. We further analyzed the function of JcCYP735A using the CRISPR-Cas9 system, and found that the concentrations of tZ and tZ-riboside decreased significantly in the Jccyp735a mutants, which showed severely retarded growth. These findings will be helpful for further studies of the functions of cytokinin metabolic genes and understanding the roles of cytokinins in Jatropha growth and development.

The landscape of cytokinin binding by a plant nodulin

Energy Technology Data Exchange (ETDEWEB)

Ruszkowski, M.; Szpotkowski, K.; Sikorski, M. [Polish Academy of Sciences, Poznan (Poland); Jaskolski, M., E-mail: mariuszj@amu.edu.pl [Polish Academy of Sciences, Poznan (Poland); A. Mickiewicz University, Poznan (Poland)

2013-12-01

The crystal structures of complexes of M. truncatula nodulin 13 with four cytokinins, trans-zeatin, N{sup 6}-isopentenyladenine, kinetin and N{sup 6}-benzyladenine, show an unusual mode of dimerization of this PR-10-fold plant protein. The cytokinin-binding mode in the internal cavity of the protein is the same in each complex and resembles the pattern found in the cytokinin receptor protein. Nodulation is an extraordinary symbiotic interaction between leguminous plants and nitrogen-fixing bacteria (rhizobia) that assimilate atmospheric nitrogen (in root nodules) and convert it into compounds suitable for the plant host. A class of plant hormones called cytokinins are involved in the nodulation process. In the model legume Medicago truncatula, nodulin 13 (MtN13), which belongs to the pathogenesis-related proteins of class 10 (PR-10), is expressed in the outer cortex of the nodules. In general, PR-10 proteins are small and monomeric and have a characteristic fold with an internal hydrophobic cavity formed between a seven-stranded antiparallel β-sheet and a C-terminal α-helix. Previously, some PR-10 proteins not related to nodulation were found to bind cytokinins such as trans-zeatin. Here, four crystal structures of the MtN13 protein are reported in complexes with several cytokinins, namely trans-zeatin, N{sup 6}-isopentenyladenine, kinetin and N{sup 6}-benzyladenine. All four phytohormones are bound in the hydrophobic cavity in the same manner and have excellent definition in the electron-density maps. The binding of the cytokinins appears to be strong and specific and is reinforced by several hydrogen bonds. Although the binding stoichiometry is 1:1, the complex is actually dimeric, with a cytokinin molecule bound in each subunit. The ligand-binding site in each cavity is formed with the participation of a loop element from the other subunit, which plugs the only entrance to the cavity. Interestingly, a homodimer of MtN13 is also formed in solution, as confirmed

Structural characterization of tartrate dehydrogenase: a versatile enzyme catalyzing multiple reactions

International Nuclear Information System (INIS)

Malik, Radhika; Viola, Ronald E.

2010-01-01

The first structure of an NAD-dependent tartrate dehydrogenase (TDH) has been solved to 2 (angstrom) resolution by single anomalous diffraction (SAD) phasing as a complex with the intermediate analog oxalate, Mg 2+ and NADH. This TDH structure from Pseudomonas putida has a similar overall fold and domain organization to other structurally characterized members of the hydroxy-acid dehydrogenase family. However, there are considerable differences between TDH and these functionally related enzymes in the regions connecting the core secondary structure and in the relative positioning of important loops and helices. The active site in these complexes is highly ordered, allowing the identification of the substrate-binding and cofactor-binding groups and the ligands to the metal ions. Residues from the adjacent subunit are involved in both the substrate and divalent metal ion binding sites, establishing a dimer as the functional unit and providing structural support for an alternating-site reaction mechanism. The divalent metal ion plays a prominent role in substrate binding and orientation, together with several active-site arginines. Functional groups from both subunits form the cofactor-binding site and the ammonium ion aids in the orientation of the nicotinamide ring of the cofactor. A lysyl amino group (Lys192) is the base responsible for the water-mediated proton abstraction from the C2 hydroxyl group of the substrate that begins the catalytic reaction, followed by hydride transfer to NAD. A tyrosyl hydroxyl group (Tyr141) functions as a general acid to protonate the enolate intermediate. Each substrate undergoes the initial hydride transfer, but differences in substrate orientation are proposed to account for the different reactions catalyzed by TDH.

Coupled reactions by coupled enzymes : alcohol to lactone cascade with alcohol dehydrogenase-cyclohexanone monooxygenase fusions

NARCIS (Netherlands)

Aalbers, Friso S; Fraaije, Marco W

2017-01-01

The combination of redox enzymes for redox-neutral cascade reactions has received increasing appreciation. An example is the combination of an alcohol dehydrogenase (ADH) with a cyclohexanone monooxygenase (CHMO). The ADH can use NADP(+) to oxidize cyclohexanol to form cyclohexanone and NADPH. Both

Transgenic barley overexpressing a cytokinin dehydrogenase gene shows greater tolerance to drought stress

Czech Academy of Sciences Publication Activity Database

Pospíšilová, H.; Jiskrová, E.; Vojta, P.; Mrízová, K.; Kokáš, F.; Majeská Čudějková, M.; Bergougnoux, V.; Plíhal, O.; Klimešová, J.; Novák, Ondřej; Dzurová, L.; Frébort, I.; Galuszka, P.

2016-01-01

Roč. 33, č. 5 (2016), s. 692-705 ISSN 1871-6784 R&D Projects: GA MŠk(CZ) LO1204 Institutional support: RVO:61389030 Keywords : ROOT-GROWTH * OXIDASE/DEHYDROGENASE GENES * BETA-GLUCOSIDASE Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.813, year: 2016

Cytokinins and urea derivatives stimulate seed germination in Lotus corniculatus L.

Directory of Open Access Journals (Sweden)

Nikolić Radomirka

2007-01-01

Full Text Available We studied the effects of various cytokinins and urea derivatives on germination of aged seeds of in Lotus corniculatus L. The following substances were applied: N6-isoprenoid cytokinins (isopentenyl adenine and zeatin, adenine sulfate, N6-aromatic cytokinins (kinetin, benzyladenine and their N9-ribosides, N-benzyl-9-(2- tetrahydropyranyladenine, and urea derivatives (diphenylurea, thidiazuron, and chloro-pyridyl phenylurea. With the exception of adenine sulfate, all cytokinins increased the percentage of seed germination up to twofold, depending on their kind and concentration. It is concluded that cytokinins may be among the missing factors in aged seeds of L. corniculatus contributing to the implementation of their full germination potential. They could be used to improve germination of both freshly harvested and aged seed samples, if necessary. .

Vanillin formation from ferulic acid in Vanilla planifolia is catalysed by a single enzyme

DEFF Research Database (Denmark)

Gallage, Nethaji J; Hansen, Esben H; Kannangara, Rubini

2014-01-01

Vanillin is a popular and valuable flavour compound. It is the key constituent of the natural vanilla flavour obtained from cured vanilla pods. Here we show that a single hydratase/lyase type enzyme designated vanillin synthase (VpVAN) catalyses direct conversion of ferulic acid and its glucoside...... to the inner part of the vanilla pod and high transcript levels are found in single cells located a few cell layers from the inner epidermis. Transient expression of VpVAN in tobacco and stable expression in barley in combination with the action of endogenous alcohol dehydrogenases and UDP...

Reaction rate studies of glucose-6-phosphate dehydrogenase activity in sections of rat liver using four tetrazolium salts

NARCIS (Netherlands)

Butcher, R. G.; van Noorden, C. J.

1985-01-01

The reaction rate of glucose-6-phosphate dehydrogenase activity in liver sections from fed and starved rats has been monitored by the continuous measurement at 37 degrees C of the reaction product as it is formed using scanning and integrating microdensitometry. Control media lacked either substrate

Uncatalysed and potassium-catalysed pyrolysis of the cell-wall constituents of biomass and their model compounds

Energy Technology Data Exchange (ETDEWEB)

Nowakowski, Daniel J.; Jones, Jenny M. [Energy and Resources Research Institute, School of Process, Environmental and Materials Engineering (SPEME), University of Leeds, Leeds, LS2 9JT (United Kingdom)

2008-09-15

Cell-wall components (cellulose, hemicellulose (oat spelt xylan), lignin (Organosolv)), and model compounds (levoglucosan (an intermediate product of cellulose decomposition) and chlorogenic acid (structurally similar to lignin polymer units)) have been investigated to probe in detail the influence of potassium on their pyrolysis behaviours as well as their uncatalysed decomposition reaction. Cellulose and lignin were pretreated to remove salts and metals by hydrochloric acid, and this dematerialized sample was impregnated with 1% of potassium as potassium acetate. Levoglucosan, xylan and chlorogenic acid were mixed with CH{sub 3}COOK to introduce 1% K. Characterisation was performed using thermogravimetric analysis (TGA) and differential thermal analysis (DTA). In addition to the TGA pyrolysis, pyrolysis-gas chromatography-mass spectrometry (PY-GC-MS) analysis was introduced to examine reaction products. Potassium-catalysed pyrolysis has a huge influence on the char formation stage and increases the char yields considerably (from 7.7% for raw cellulose to 27.7% for potassium impregnated cellulose; from 5.7% for raw levoglucosan to 20.8% for levoglucosan with CH{sub 3}COOK added). Major changes in the pyrolytic decomposition pathways were observed for cellulose, levoglucosan and chlorogenic acid. The results for cellulose and levoglucosan are consistent with a base catalysed route in the presence of the potassium salt which promotes complete decomposition of glucosidic units by a heterolytic mechanism and favours its direct depolymerization and fragmentation to low molecular weight components (e.g. acetic acid, formic acid, glyoxal, hydroxyacetaldehyde and acetol). Base catalysed polymerization reactions increase the char yield. Potassium-catalysed lignin pyrolysis is very significant: the temperature of maximum conversion in pyrolysis shifts to lower temperature by 70 K and catalysed polymerization reactions increase the char yield from 37% to 51%. A similar trend

Programmed cell death induced by high levels of cytokinin in Arabidopsis cultured cells is mediated by the cytokinin receptor CRE1/AHK4

Czech Academy of Sciences Publication Activity Database

Vescovi, M.; Riefler, M.; Gessuti, M.; Novák, Ondřej; Schmülling, T.; Lo Schiavo, F.

2012-01-01

Roč. 63, č. 7 (2012), s. 2825-2832 ISSN 0022-0957 Institutional research plan: CEZ:AV0Z50380511 Keywords : Arabidopsis cultured cells * cytokinin * histidine kinase cytokinin receptors Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 5.242, year: 2012

Characterising Complex Enzyme Reaction Data.

Directory of Open Access Journals (Sweden)

Handan Melike Dönertaş

Full Text Available The relationship between enzyme-catalysed reactions and the Enzyme Commission (EC number, the widely accepted classification scheme used to characterise enzyme activity, is complex and with the rapid increase in our knowledge of the reactions catalysed by enzymes needs revisiting. We present a manual and computational analysis to investigate this complexity and found that almost one-third of all known EC numbers are linked to more than one reaction in the secondary reaction databases (e.g., KEGG. Although this complexity is often resolved by defining generic, alternative and partial reactions, we have also found individual EC numbers with more than one reaction catalysing different types of bond changes. This analysis adds a new dimension to our understanding of enzyme function and might be useful for the accurate annotation of the function of enzymes and to study the changes in enzyme function during evolution.

Manganese-catalysed benzylic C(sp3)-H amination for late-stage functionalization.

Science.gov (United States)

Clark, Joseph R; Feng, Kaibo; Sookezian, Anasheh; White, M Christina

2018-06-01

Reactions that directly install nitrogen into C-H bonds of complex molecules are significant because of their potential to change the chemical and biological properties of a given compound. Although selective intramolecular C-H amination reactions are known, achieving high levels of reactivity while maintaining excellent site selectivity and functional-group tolerance remains a challenge for intermolecular C-H amination. Here, we report a manganese perchlorophthalocyanine catalyst [MnIII(ClPc)] for intermolecular benzylic C-H amination of bioactive molecules and natural products that proceeds with unprecedented levels of reactivity and site selectivity. In the presence of a Brønsted or Lewis acid, the [MnIII(ClPc)]-catalysed C-H amination demonstrates unique tolerance for tertiary amine, pyridine and benzimidazole functionalities. Mechanistic studies suggest that C-H amination likely proceeds through an electrophilic metallonitrene intermediate via a stepwise pathway where C-H cleavage is the rate-determining step of the reaction. Collectively, these mechanistic features contrast with previous base-metal-catalysed C-H aminations and provide new opportunities for tunable selectivities.

Potential application of urea-derived herbicides as cytokinins in ...

Indian Academy of Sciences (India)

... the frequency of regeneration was 90% with a mean number of 6 shoots. Diuron with two chloride groups in the phenyl ring showed significantly higher cytokinin-like activity than single chloride substitution monuron. This study demonstrates the potential use of monuron and diuron as cytokinins in plant tissue culture.

Arabidopsis ABCG14 protein controls the acropetal translocation of root-synthesized cytokinins

Science.gov (United States)

Zhang, Kewei; Novak, Ondrej; Wei, Zhaoyang; Gou, Mingyue; Zhang, Xuebin; Yu, Yong; Yang, Huijun; Cai, Yuanheng; Strnad, Miroslav; Liu, Chang-Jun

2014-02-01

Cytokinins are a major group of phytohormones regulating plant growth, development and stress responses. However, in contrast to the well-defined polar transport of auxins, the molecular basis of cytokinin transport is poorly understood. Here we show that an ATP-binding cassette transporter in Arabidopsis, AtABCG14, is essential for the acropetal (root to shoot) translocation of the root-synthesized cytokinins. AtABCG14 is expressed primarily in the pericycle and stelar cells of roots. Knocking out AtABCG14 strongly impairs the translocation of trans-zeatin (tZ)-type cytokinins from roots to shoots, thereby affecting the plant’s growth and development. AtABCG14 localizes to the plasma membrane of transformed cells. In planta feeding of C14 or C13-labelled tZ suggests that it acts as an efflux pump and its presence in the cells directly correlates with the transport of the fed cytokinin. Therefore, AtABCG14 is a transporter likely involved in the long-distance translocation of cytokinins in planta.

The crystal structure of Lactococcus lactis dihydroorotate dehydrogenase A complexed with the enzyme reaction product throws light on its enzymatic function

DEFF Research Database (Denmark)

Rowland, Paul; Bjørnberg, Olof; Nielsen, Finn S.

1998-01-01

Dihydroorotate dehydrogenases (DHODs) catalyze the oxidation of (S)-dihydroorotate to orotate, the fourth step and only redox reaction in the de novo biosynthesis of pyrimidine nucleotides. A description is given of the crystal structure of Lactococcus lactis dihydroorotate dehydrogenase A (DHODA......) complexed with the product of the enzyme reaction orotate. The structure of the complex to 2.0 A resolution has been compared with the structure of the native enzyme. The active site of DHODA is known to contain a water filled cavity buried beneath a highly conserved and flexible loop. In the complex...

Developmental changes in rat liver branched-chain 2-oxo acid dehydrogenase.

OpenAIRE

May, E E; May, M E; Aftring, R P; Buse, M G

1982-01-01

Branched-chain 2-oxo acid dehydrogenase catalyses the first irreversible step in the degradation of the branched-chain amino acids leucine, isoleucine and valine. With specifically labelled 4-methyl-2-oxo[1-14C]pentanoate as substrate, the enzyme's activity was measured in rat liver homogenates. Activity (per g wet wL of liver or per mg of protein) increased most rapidly during the perinatal period (2 days before to 1 day after birth), reaching approximately adult values by the time of weanin...

Bioacetylation of alcohols catalysed by Saccharum officinarum; Bioacetilacao de alcoois catalisada por Saccharum officinarum

Energy Technology Data Exchange (ETDEWEB)

Assuncao, Joao Carlos C.; Lemos, Telma Leda G.; Monte, Francisco Jose Q. [Universidade Federal do Ceara (UFC), Fortaleza, CE (Brazil). Dept. de Quimica Organica e Inorganica], e-mail: fmonte@dqoi.ufc.br

2009-07-01

Lipase-catalysed esterifications of alcohols using immobilized enzyme system from sugar cane (Saccharum officinarum) as biocatalyst afforded the corresponding esters in considerable yields (68-93%). Under optimized conditions, the material was utilized for reactions of acetylation with several advantage. It also investigated the possibility of reuse of immobilized enzymes of S. officinarum as biocatalyst under optimal reaction conditions. (author)

Ultrasonic enhancement of lipase-catalysed transesterification for biodiesel synthesis.

Science.gov (United States)

Bhangu, Sukhvir Kaur; Gupta, Shweta; Ashokkumar, Muthupandian

2017-01-01

The production of biodiesel was carried out from canola oil and methanol catalysed by lipase from Candida rugosa under different ultrasonic experimental conditions using horn (20kHz) and plate (22, 44, 98 and 300kHz) transducers. The effects of experimental conditions such as horn tip diameter, ultrasonic power, ultrasonic frequency and enzyme concentrations on biodiesel yield were investigated. The results showed that the application of ultrasound decreased the reaction time from 22-24h to 1.5h with the use of 3.5cm ultrasonic horn, an applied power of 40W, methanol to oil molar ratio of 5:1 and enzyme concentration of 0.23wt/wt% of oil. Low intensity ultrasound is efficient and a promising tool for the enzyme catalysed biodiesel synthesis as higher intensities tend to inactivate the enzyme and reduce its efficiency. Copyright © 2016 Elsevier B.V. All rights reserved.

Cytokinin Cross-talking During Biotic and Abiotic Stress Responses

Directory of Open Access Journals (Sweden)

Jose Antonio O'Brien

2013-11-01

Full Text Available As sessile organisms, plants have to be able to adapt to a continuously changing environment. Plants that perceive some of these changes as stress signals activate signaling pathways to modulate their development and to enable them to survive. The complex responses to environmental cues are to a large extent mediated by plant hormones that together orchestrate the final plant response. The phytohormone cytokinin is involved in many plant developmental processes. Recently, it has been established that cytokinin plays an important role in stress responses, but does not act alone. Indeed, the hormonal control of plant development and stress adaptation is the outcome of a complex network of multiple synergistic and antagonistic interactions between various hormones. Here, we review the recent findings on the cytokinin function as part of this hormonal network. We focus on the importance of the crosstalk between cytokinin and other hormones, such as abscisic acid, jasmonate, salicylic acid, ethylene, and auxin in the modulation of plant development and stress adaptation. Finally, the impact of the current research in the biotechnological industry will be discussed.

The Role of Cytokinin During Infection of Arabidopsis thaliana by the Cyst Nematode Heterodera schachtii.

Science.gov (United States)

Shanks, Carly M; Rice, J Hollis; Zubo, Yan; Schaller, G Eric; Hewezi, Tarek; Kieber, Joseph J

2016-01-01

Plant-parasitic cyst nematodes induce the formation of hypermetabolic feeding sites, termed syncytia, as their sole source of nutrients. The formation of the syncytium is orchestrated by the nematode, in part, by modulation of phytohormone responses, including cytokinin. In response to infection by the nematode Heterodera schachtii, cytokinin signaling is transiently induced at the site of infection and in the developing syncytium. Arabidopsis lines with reduced cytokinin sensitivity show reduced susceptibility to nematode infection, indicating that cytokinin signaling is required for optimal nematode development. Furthermore, lines with increased cytokinin sensitivity also exhibit reduced nematode susceptibility. To ascertain why cytokinin hypersensitivity reduces nematode parasitism, we examined the transcriptomes in wild type and a cytokinin-hypersensitive type-A arr Arabidopsis mutant in response to H. schachtii infection. Genes involved in the response to biotic stress and defense response were elevated in the type-A arr mutant in the absence of nematodes and were hyperinduced following H. schachtii infection, which suggests that the Arabidopsis type-A arr mutants impede nematode development because they are primed to respond to pathogen infection. These results suggest that cytokinin signaling is required for optimal H. schachtii parasitism of Arabidopsis but that elevated cytokinin signaling triggers a heightened immune response to nematode infection.

Chemical kinetics: on the heterogeneous catalysis processes leading to an exchange between two phases. Example: isotopic exchange reactions; Cinetique chimique: sur les processus de catalyse 'heterogene' conduisant a un echange entre deux phases. Exemple: reactions d'echange isotopique

Energy Technology Data Exchange (ETDEWEB)

Dirian, G; Grandcollot, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

1961-07-01

For an exchange reaction between a gaseous and a liquid phase proceeding by 'heterogeneous' catalysis in the liquid phase, diffusion in the liquid and the chemical reaction are two simultaneous and indivisible processes. We have nevertheless been able to establish criteria making it possible to distinguish between a really homogeneous kinetic process and a pseudo-homogeneous one. (author) [French] Pour une reaction d'echange entre une phase gazeuse et une phase liquide procedant par catalyse 'heterogene' en phase liquide, la diffusion dans le liquide et la reaction chimique sont deux etapes simultanees et indissociables. Nous avons pu neanmoins etablir des criteres permettant de distinguer entre une cinetique homogene vraie et une cinetique pseudo-homogene. (auteur)

Effects of auxins and cytokinins on tomato callus from anthers

Directory of Open Access Journals (Sweden)

Janina H. Rogozińska

2015-01-01

Full Text Available An investigation was carried out on growth substance requirements of tomato callus derived from anthers for culture in vitro. Linsmaier and Skoog (1965 medium was used with various levels of auxins (IAA and NAA and cytokinins (K and BAP. The results show that cytokinin is an absolute requirement for callus growth irrespective of the auxin level. The optimum concentration of auxin in combination with cytokinin was found to be 5 μM of NAA or 25 μM of IAA, with 5 μM of K or BAP. Callus growth on media with NAA and cytokinin was superior to that on IAA, amounting to 6.05 g per piece on medium with 5 μM of NAA and BAP. Tissues grown on this medium have the highest water content. At the onset of culture the tissue is characterized by weak growth and attains its maximal increase in fresh weight after 6 weeks.

Structure sensitivity in the nonscalable regime explored via catalysed ethylene hydrogenation on supported platinum nanoclusters

Science.gov (United States)

Crampton, Andrew S.; Rötzer, Marian D.; Ridge, Claron J.; Schweinberger, Florian F.; Heiz, Ueli; Yoon, Bokwon; Landman, Uzi

2016-01-01

The sensitivity, or insensitivity, of catalysed reactions to catalyst structure is a commonly employed fundamental concept. Here we report on the nature of nano-catalysed ethylene hydrogenation, investigated through experiments on size-selected Ptn (n=8-15) clusters soft-landed on magnesia and first-principles simulations, yielding benchmark information about the validity of structure sensitivity/insensitivity at the bottom of the catalyst size range. Both ethylene-hydrogenation-to-ethane and the parallel hydrogenation-dehydrogenation ethylidyne-producing route are considered, uncovering that at the =10) clusters at T>150 K, with maximum room temperature reactivity observed for Pt13. Structure insensitivity, inherent for specific cluster sizes, is induced in the more active Pt13 by a temperature increase up to 400 K leading to ethylidyne formation. Control of sub-nanometre particle size may be used for tuning catalysed hydrogenation activity and selectivity.

Microscale magnetic microparticle-based immunopurification of cytokinins from Arabidopsis root apex

Czech Academy of Sciences Publication Activity Database

Plačková, Lenka; Oklešťková, Jana; Pospíšková, K.; Poláková, K.; Buček, J.; Stýskala, J.; Zatloukal, M.; Šafařík, Ivo; Zbořil, R.; Strnad, Miroslav; Doležal, Karel; Novák, Ondřej

2017-01-01

Roč. 89, č. 5 (2017), s. 1065-1075 ISSN 0960-7412 R&D Projects: GA MŠk(CZ) LO1204; GA MŠk LK21306; GA ČR GA14-34792S Institutional support: RVO:61389030 ; RVO:60077344 Keywords : solid-phase extraction * tandem mass-spectrometry * endogenous cytokinins * plant-samples * cis-zeatin * quantitative-analysis * aromatic cytokinins * abscisic-acid * oryza-sativa * purification * cytokinins * magnetic microparticles * immunoaffinity separation * metabolite profiling * Arabidopsis thaliana * technical advance Subject RIV: EB - Genetics ; Molecular Biology OBOR OECD: Plant sciences, botany Impact factor: 5.901, year: 2016

SCF(KMD) controls cytokinin signaling by regulating the degradation of type-B response regulators.

Science.gov (United States)

Kim, Hyo Jung; Chiang, Yi-Hsuan; Kieber, Joseph J; Schaller, G Eric

2013-06-11

Cytokinins are plant hormones that play critical roles in growth and development. In Arabidopsis, the transcriptional response to cytokinin is regulated by action of type-B Arabidopsis response regulators (ARRs). Although central elements in the cytokinin signal transduction pathway have been identified, mechanisms controlling output remain to be elucidated. Here we demonstrate that a family of F-box proteins, called the kiss me deadly (KMD) family, targets type-B ARR proteins for degradation. KMD proteins form an S-phase kinase-associated PROTEIN1 (SKP1)/Cullin/F-box protein (SCF) E3 ubiquitin ligase complex and directly interact with type-B ARR proteins. Loss-of-function KMD mutants stabilize type-B ARRs and exhibit an enhanced cytokinin response. In contrast, plants with elevated KMD expression destabilize type-B ARR proteins leading to cytokinin insensitivity. Our results support a model in which an SCF(KMD) complex negatively regulates cytokinin responses by controlling levels of a key family of transcription factors.

Novel cytokinin derivatives do not show negative effects on root growth and proliferation in submicromolar range.

Directory of Open Access Journals (Sweden)

Kateřina Podlešáková

Full Text Available BACKGROUND: When applied to a nutrition solution or agar media, the non-substituted aromatic cytokinins caused thickening and shortening of the primary root, had an inhibitory effect on lateral root branching, and even showed some negative effects on development of the aerial part at as low as a 10 nanomolar concentration. Novel analogues of aromatic cytokinins ranking among topolins substituted on N9-atom of adenine by tetrahydropyranyl or 4-chlorobutyl group have been prepared and tested in standardized cytokinin bioassays [1]. Those showing comparable activities with N(6-benzylaminopurine were further tested in planta. METHODOLOGY/PRINCIPAL FINDINGS: The main aim of the study was to explain molecular mechanism of function of novel cytokinin derivatives on plant development. Precise quantification of cytokinin content and profiling of genes involved in cytokinin metabolism and perception in treated plants revealed several aspects of different action of m-methoxytopolin base and its substituted derivative on plant development. In contrast to standard cytokinins, N9- tetrahydropyranyl derivative of m-topolin and its methoxy-counterpart showed the negative effects on root development only at three orders of magnitude higher concentrations. Moreover, the methoxy-derivative demonstrates a positive effect on lateral root branching and leaf emerging in a nanomolar range of concentrations, in comparison with untreated plants. CONCLUSIONS/SIGNIFICANCE: Tetrahydropyranyl substitution at N9-position of cytokinin purine ring significantly enhances acropetal transport of a given cytokinins. Together with the methoxy-substitution, impedes accumulation of non-active cytokinin glucoside forms in roots, allows gradual release of the active base, and has a significant effect on the distribution and amount of endogenous isoprenoid cytokinins in different plant tissues. The utilization of novel aromatic cytokinin derivatives can distinctively improve expected

Endogenous cytokinins in three genera of microalgae from the chlorophyta

Czech Academy of Sciences Publication Activity Database

Ördög, V.; Stirk, W. A.; van Staden, J.; Novák, Ondřej; Strnad, Miroslav

2004-01-01

Roč. 40, č. 1 (2004), s. 88-95 ISSN 0022-3646 R&D Projects: GA ČR GA522/03/0323; GA AV ČR IBS5038351 Institutional research plan: CEZ:AV0Z5038910 Keywords : aromatic cytokinins * Chlorophyta * endogenous cytokinin content Subject RIV: EC - Immunology Impact factor: 2.490, year: 2004

Sn-Beta catalysed conversion of hemicellulosic sugars

DEFF Research Database (Denmark)

Holm, Martin; Pagán-Torres, Yomaira J.; Shunmugavel, Saravanamurugan

2012-01-01

are observed for the pentoses. This finding is in accordance to a reaction pathway that involves the retro aldol condensation of the sugars to form a triose and glycolaldehyde for the pentoses, and two trioses for hexoses. When reacting glycolaldehyde (formally a C2-sugar) in the presence of Sn-Beta, aldol...... condensation occurs, leading to the formation of methyl lactate, methyl vinylglycolate and methyl 2-hydroxy-4-methoxybutanoate. In contrast, when converting the sugars in water at low temperatures (100 °C), Sn-Beta catalyses the isomerisation of sugars (ketose–aldose epimers), rather than the formation...

Endogenous cytokinin overproduction modulates ROS homeostasis and decreases salt stress resistance in Arabidopsis thaliana

Directory of Open Access Journals (Sweden)

Yanping eWang

2015-11-01

Full Text Available Cytokinins in plants are crucial for numerous biological processes, including seed germination, cell division and differentiation, floral initiation and adaptation to abiotic stresses. The salt stress can promote reactive oxygen species (ROS production in plants which are highly toxic and ultimately results in oxidative stress. However, the correlation between endogenous cytokinin production and ROS homeostasis in responding to salt stress is poorly understood. In this study, we analyzed the correlation of overexpressing the cytokinin biosynthetic gene AtIPT8 (adenosine phosphate-isopentenyl transferase 8 and the response of salt stress in Arabidopsis. Overproduction of cytokinins, which was resulted by the inducible overexpression of AtIPT8, significantly inhibited the primary root growth and true leaf emergence, especially under the conditions of exogenous salt, glucose and mannitol treatments. Upon cytokinin overproduction, the salt stress resistance was declined, and resulted in less survival rates and chlorophyll content. Interestingly, ROS production was obviously increased with the salt treatment, accompanied by endogenously overproduced cytokinins. The activities of CAT and SOD, which are responsible for scavenging ROS, were also affected. Transcription profiling revealed that the differential expressions of ROS-producing and scavenging related genes, the photosynthesis-related genes and stress responsive genes were existed in transgenic plants of overproducing cytokinins. Our results suggested that broken in the homeostasis of cytokinins in plant cells could modulate the salt stress responses through a ROS-mediated regulation in Arabidopsis.

The cereal pathogen Fusarium pseudograminearum produces a new class of active cytokinins during infection

DEFF Research Database (Denmark)

Sørensen, Jens Laurids; Benfield, Aurelie H.; Wollenberg, Rasmus Dam

2018-01-01

-senescence activities and the production of a cytokinin mimic by what was once considered a necrotrophic pathogen that promotes cell death and senescence challenges the simple view that this pathogen invades its hosts by employing a barrage of lytic enzymes and toxins. Through genome mining, a gene cluster in the F....... pseudograminearum genome for the production of Fusarium cytokinins was identified and the biosynthetic pathway established using gene knockouts. The Fusarium cytokinins could activate plant cytokinin signalling, demonstrating their genuine hormone mimicry. In planta analysis of the transcriptional response to one...

The use of cultivars of Raphanus sativus for cytokinin bioassay

Directory of Open Access Journals (Sweden)

Dorota Kubowicz

2013-12-01

Full Text Available Six cultivars of radish (Raphanus sativus were tested for their usefulness in radish cytokinin bioassay by the method of Letham (1971. The best cultivar was found to be 'Sopel Lodu' which responds well to both zeatin and 2iP over a wide range of concentrations. The fresh weight of cotyledons increased at most by 71.5% (if treated with zeatin or 101.0% (if treated with 2iP compared to untreated cotyledons. This cultivar is also sensitive to the partially purified cytokinin-like fraction isolated from the pine (Pinus silvestris cambial region. The cultivar 'Sopel Lodu' is therefore proposed to be a suitable plant for cytokinin bioassays.

Characterization of a Cytokinin Response Factor in Arabidopsis thaliana

OpenAIRE

Ketelsen, Bernd

2012-01-01

The papers of this thesis are not available in Munin: 1. Bernd Ketelsen, Rainer Schwacke, Kirsten Krause and Karsten Fischer: 'Transcriptional activation by Cytokinin Response Factor 5 is governed by an acidic Cterminus containing two conserved domains' (manuscript) 2. Bernd Ketelsen, Stian Olsen, Kirsten Krause and Karsten Fischer: 'Cytokinin responsive factor 5 (CRF5) is involved in root development, hormonal crosstalk and sugar metabolism in Arabidopsis thaliana' (manuscript) 3. Bernd K...

Preparation, characterization and biological activity of C8-substituted cytokinins

Czech Academy of Sciences Publication Activity Database

Zahajská, Lenka; Nisler, Jaroslav; Voller, Jiří; Gucký, Tomáš; Pospíšil, Tomáš; Spíchal, Lukáš; Strnad, Miroslav

2017-01-01

Roč. 135, MAR (2017), s. 115-127 ISSN 0031-9422 Institutional support: RVO:61389030 Keywords : potential purine antagonists * arabidopsis-thaliana * nucleosides * derivatives * thidiazuron * specificity * receptors * kinetin * Organic synthesis * Cytokinin bioassay * AHK3 and CRE1/AHK4 bacterial receptor assay * C8-substituted cytokinin Subject RIV: CE - Biochemistry OBOR OECD: Organic chemistry Impact factor: 3.205, year: 2016

Abscisic Acid-Cytokinin Antagonism Modulates Resistance Against Pseudomonas syringae in Tobacco.

Science.gov (United States)

Großkinsky, Dominik K; van der Graaff, Eric; Roitsch, Thomas

2014-12-01

Phytohormones are known as essential regulators of plant defenses, with ethylene, jasmonic acid, and salicylic acid as the central immunity backbone, while other phytohormones have been demonstrated to interact with this. Only recently, a function of the classic phytohormone cytokinin in plant immunity has been described in Arabidopsis, rice, and tobacco. Although interactions of cytokinins with salicylic acid and auxin have been indicated, the complete network of cytokinin interactions with other immunity-relevant phytohormones is not yet understood. Therefore, we studied the interaction of kinetin and abscisic acid as a negative regulator of plant immunity to modulate resistance in tobacco against Pseudomonas syringae. By analyzing infection symptoms, pathogen proliferation, and accumulation of the phytoalexin scopoletin as a key mediator of kinetin-induced resistance in tobacco, antagonistic interaction of these phytohormones in plant immunity was identified. Kinetin reduced abscisic acid levels in tobacco, while increased abscisic acid levels by exogenous application or inhibition of abscisic acid catabolism by diniconazole neutralized kinetin-induced resistance. Based on these results, we conclude that reduction of abscisic acid levels by enhanced abscisic acid catabolism strongly contributes to cytokinin-mediated resistance effects. Thus, the identified cytokinin-abscisic acid antagonism is a novel regulatory mechanism in plant immunity.

Silver triflate/p-TSA co-catalysed synthesis of 3-substituted isocoumarins from 2-alkynylbenzoates.

Science.gov (United States)

Gianni, Jonathan; Pirovano, Valentina; Abbiati, Giorgio

2018-05-02

In this paper, we describe the silver triflate/p-toluenesulfonic acid co-catalysed synthesis of seventeen isocoumarins and two thieno[2,3-c]pyran-7-ones starting from 2-alkynylbenzoates and 3-alkynylthiophene-2-carboxylates, respectively. The reaction proceeds with absolute regioselectivity under mild reaction conditions and low catalyst loading, to afford the desired products in good to excellent yields. A conceivable reaction mechanism is proposed and supported by isotope-exchange tests, 1H NMR studies and ad hoc experiments.

Shikimate dehydrogenase from Pinu sylvestris L. needles

International Nuclear Information System (INIS)

Osipov, V.I.; Shein, I.V.

1986-01-01

Shikimate dehydrogenase was isolated by extraction from pine needles and partially purified by fractionation with ammonium sulfate. In conifers, in contrast to other plants, all three isoenzymes of shikimate dehydrogenase exhibit activity not only with NADP + , but also with NAD + . The values of K/sub m/ for shikimate, when NADP + and NAD + are used as cofactors, are 0.22 and 1.13 mM, respectively. The enzyme is maximally active at pH 10 with both cofactors. It is suggested that NAD-dependent shikimate dehydrogenase catalyzes the initial reaction of the alternative pathway of the conversion of shikimic acid to hydroxybenzoic acid. The peculiarities of the organization and regulation of the initial reactions of the shikimate pathway in conifers and in plants with shikimate dehydrogenase absolutely specific for NADP are discussed

Plant hormone cytokinins control cell cycle progression and plastid replication in apicomplexan parasites.

Science.gov (United States)

Andrabi, Syed Bilal Ahmad; Tahara, Michiru; Matsubara, Ryuma; Toyama, Tomoko; Aonuma, Hiroka; Sakakibara, Hitoshi; Suematsu, Makoto; Tanabe, Kazuyuki; Nozaki, Tomoyoshi; Nagamune, Kisaburo

2018-02-01

Cytokinins are plant hormones that are involved in regulation of cell proliferation, cell cycle progression, and cell and plastid development. Here, we show that the apicomplexan parasites Toxoplasma gondii and Plasmodium berghei, an opportunistic human pathogen and a rodent malaria agent, respectively, produce cytokinins via a biosynthetic pathway similar to that in plants. Cytokinins regulate the growth and cell cycle progression of T. gondii by mediating expression of the cyclin gene TgCYC4. A natural form of cytokinin, trans-zeatin (t-zeatin), upregulated expression of this cyclin, while a synthetic cytokinin, thidiazuron, downregulated its expression. Immunofluorescence microscopy and quantitative PCR analysis showed that t-zeatin increased the genome-copy number of apicoplast, which are non-photosynthetic plastid, in the parasite, while thidiazuron led to their disappearance. Thidiazuron inhibited growth of T. gondii and Plasmodium falciparum, a human malaria parasite, suggesting that thidiazuron has therapeutic potential as an inhibitor of apicomplexan parasites. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Rieske non-heme iron-dependent oxygenases catalyse diverse reactions in natural product biosynthesis.

Science.gov (United States)

Perry, Christopher; de Los Santos, Emmanuel L C; Alkhalaf, Lona M; Challis, Gregory L

2018-04-13

Covering: up to the end of 2017The roles played by Rieske non-heme iron-dependent oxygenases in natural product biosynthesis are reviewed, with particular focus on experimentally characterised examples. Enzymes belonging to this class are known to catalyse a range of transformations, including oxidative carbocyclisation, N-oxygenation, C-hydroxylation and C-C desaturation. Examples of such enzymes that have yet to be experimentally investigated are also briefly described and their likely functions are discussed.

Transient accumulation of cis- and trans-zeatin type cytokinins and its relation to cytokinin oxidase activity during cell cycle of synchronized tobacco BY-2 cells

Czech Academy of Sciences Publication Activity Database

Dobrev, Petre; Motyka, Václav; Gaudinová, Alena; Malbeck, Jiří; Trávníčková, Alena; Kamínek, Miroslav; Vaňková, Radomíra

2002-01-01

Roč. 40, - (2002), s. 333-337 ISSN 0981-9428 R&D Projects: GA ČR GA522/99/1130; GA ČR GV206/96/K188; GA AV ČR IAA6038002 Institutional research plan: CEZ:AV0Z5038910 Keywords : Cis zeatin * Cytokinins * Cytokinin oxidase Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 1.582, year: 2002

Transcript profiling of cytokinin action in Arabidopsis roots and shoots discovers largely similar but also organ-specific responses

Directory of Open Access Journals (Sweden)

Brenner Wolfram G

2012-07-01

Full Text Available Abstract Background The plant hormone cytokinin regulates growth and development of roots and shoots in opposite ways. In shoots it is a positive growth regulator whereas it inhibits growth in roots. It may be assumed that organ-specific regulation of gene expression is involved in these differential activities, but little is known about it. To get more insight into the transcriptional events triggered by cytokinin in roots and shoots, we studied genome-wide gene expression in cytokinin-treated and cytokinin-deficient roots and shoots. Results It was found by principal component analysis of the transcriptomic data that the immediate-early response to a cytokinin stimulus differs from the later response, and that the transcriptome of cytokinin-deficient plants is different from both the early and the late cytokinin induction response. A higher cytokinin status in the roots activated the expression of numerous genes normally expressed predominantly in the shoot, while a lower cytokinin status in the shoot reduced the expression of genes normally more active in the shoot to a more root-like level. This shift predominantly affected nuclear genes encoding plastid proteins. An organ-specific regulation was assigned to a number of genes previously known to react to a cytokinin signal, including root-specificity for the cytokinin hydroxylase gene CYP735A2 and shoot specificity for the cell cycle regulator gene CDKA;1. Numerous cytokinin-regulated genes were newly discovered or confirmed, including the meristem regulator genes SHEPHERD and CLAVATA1, auxin-related genes (IAA7, IAA13, AXR1, PIN2, PID, several genes involved in brassinosteroid (CYP710A1, CYP710A2, DIM/DWF and flavonol (MYB12, CHS, FLS1 synthesis, various transporter genes (e.g. HKT1, numerous members of the AP2/ERF transcription factor gene family, genes involved in light signalling (PhyA, COP1, SPA1, and more than 80 ribosomal genes. However, contrasting with the fundamental difference of

Ion-tagged π-acidic alkene ligands promote Pd-catalysed allyl-aryl couplings in an ionic liquid

NARCIS (Netherlands)

Bäuerlein, P.S.; Fairlamb, I.J.S.; Jarvis, A.G.; Lee, A.F.; Müller, C.; Slattery, J.M.; Thatcher, R.J.; Vogt, D.; Whitwood, A.C.

2009-01-01

Ionic p-acidic alkene ligands based on chalcone and benzylidene acetone frameworks have been ?doped? into ionic liquids to provide functional reaction media for Pd-catalysed cross-couplings of a cyclohexenyl carbonate with aryl siloxanes that allow simple product isolation, free from Pd (

CHANGES IN THE CHARACTERISTICS OF ‘PRATA’ BANANA TREATED WITH CYTOKININ AND GIBBERELLIN

Directory of Open Access Journals (Sweden)

JULIANA DOMINGUES LIMA

Full Text Available ABSTRACT Plant growth regulators can influence fruit yield and quality. This study aimed to evaluate the effect of cytokinin and gibberelin on the agronomic and physicochemical characteristics of banana fruits cv. ‘Prata’ (Musa spp. AAB, according to the formation period and position in the bunch. The experiment was conducted in a completely randomized 2 x 5 factorial design, two periods of bunch development (summer and winter, five treatments and ten replicates. To study the effect of position in the bunch, split plot was adopted, considering in the plot, 2 x 5 factorial and in subplots, hand 1, hand 4 and last hand. Treatments consisted of 2 pulverizations with water, 150 mg L-1 cytokinin, 200 mg L-1 of gibberellic acid, 100 mg L-1 of cytokinin plus 200 mg L-1 of gibberellic acid and 200 mg L-1 of cytokinin plus 200 mg L-1 of gibberellic acid, applied from the fourth to the last hand of the bunch. Cytokinin and gibberellin, alone or associated, regardless of formation period and position, did not affect the size and physicochemical characteristics of fruits, only delayed the bunch harvest.

The platinum catalysed decomposition of hydrazine in acidic media

International Nuclear Information System (INIS)

Ananiev, A.V.; Tananaev, I.G.; Brossard, Ph.; Broudic, J.C.

2000-01-01

Kinetic study of the hydrazine decomposition in the solutions of HClO 4 , H 2 SO 4 and HNO 3 in the presence of Pt/SiO 2 catalyst has been undertaken. It was shown that the kinetics of the hydrazine catalytic decomposition in HClO 4 and H 2 SO 4 are identical. The process is determined by the heterogeneous catalytic auto-decomposition of N 2 H 4 on the catalyst's surface. The platinum catalysed hydrazine decomposition in the nitric acid solutions is a complex process, including heterogeneous catalytic auto-decomposition of N 2 H 4 , reaction of hydrazine with catalytically generated nitrous acid and the catalytic oxidation of hydrazine by nitric acid. The kinetic parameters of these reactions have been determined. The contribution of each reaction in the total process is determined by the liquid phase composition and by the temperature. (authors)

Abscisic acid-cytokinin antagonism modulates resistance against pseudomonas syringae in Tobacco

DEFF Research Database (Denmark)

Grosskinsky, Dominik Kilian; van der Graaff, Eric; Roitsch, Thomas Georg

2014-01-01

Phytohormones are known as essential regulators of plant defenses, with ethylene, jasmonic acid, and salicylic acid as the central immunity backbone, while other phytohormones have been demonstrated to interact with this. Only recently, a function of the classic phytohormone cytokinin in plant...... immunity has been described in Arabidopsis, rice, and tobacco. Although interactions of cytokinins with salicylic acid and auxin have been indicated, the complete network of cytokinin interactions with other immunity-relevant phytohormones is not yet understood. Therefore, we studied the interaction...... of kinetin and abscisic acid as a negative regulator of plant immunity to modulate resistance in tobacco against Pseudomonas syringae. By analyzing infection symptoms, pathogen proliferation, and accumulation of the phytoalexin scopoletin as a key mediator of kinetin-induced resistance in tobacco...

Auxin regulation of cytokinin biosynthesis in Arabidopsis thaliana: A factor of potential importance for auxin-cytokinin-regulated development

Czech Academy of Sciences Publication Activity Database

Nordström, A.; Tarkowski, Petr; Tarkowská, Danuše; Norbaek, R.; Astot, C.; Doležal, Karel; Sandberg, G.

2004-01-01

Roč. 101, č. 21 (2004), s. 8039-8044 ISSN 0027-8424 Institutional research plan: CEZ:AV0Z5038910 Keywords : Arabidopsis * auxin * cytokinin * biosynthesis Subject RIV: EF - Botanics Impact factor: 10.452, year: 2004

Palladium-catalysed anti-Markovnikov selective oxidative amination

Science.gov (United States)

Kohler, Daniel G.; Gockel, Samuel N.; Kennemur, Jennifer L.; Waller, Peter J.; Hull, Kami L.

2018-03-01

In recent years, the synthesis of amines and other nitrogen-containing motifs has been a major area of research in organic chemistry because they are widely represented in biologically active molecules. Current strategies rely on a multistep approach and require one reactant to be activated prior to the carbon-nitrogen bond formation. This leads to a reaction inefficiency and functional group intolerance. As such, a general approach to the synthesis of nitrogen-containing compounds from readily available and benign starting materials is highly desirable. Here we present a palladium-catalysed oxidative amination reaction in which the addition of the nitrogen occurs at the less-substituted carbon of a double bond, in what is known as anti-Markovnikov selectivity. Alkenes are shown to react with imides in the presence of a palladate catalyst to generate the terminal imide through trans-aminopalladation. Subsequently, olefin isomerization occurs to afford the thermodynamically favoured products. Both the scope of the transformation and mechanistic investigations are reported.

Cytokinins and polar transport of auxin in axillary pea buds

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Petr Kalousek

2010-01-01

Full Text Available The influence of cytokinin on auxin transport during release of axillary buds from apical dominance was studied. Expression of auxin-carrier coding genes PsAUX1 (AUXIN RESISTANT 1 and PsPIN1 (PIN-FORMED 1 was explored in axillary buds of the 2nd node of 7-day pea plants (Pisum sativum L. cv. Vladan after decapitation or after exogenous application of benzyladenine (6-benzylaminopurine onto axillary buds of intact plants. Localization of the PsPIN1 protein, the key factor for polar transport of auxin in axillary buds, was visualised by immunohistochemistry. After exogenous application of cytokinin the expression of PsAUX1 and PsPIN1 rapidly increased with a simultaneous rapid decrease in PsDRM1 and PsAD1 expression – genes related to bud dormancy. The same changes in expression were observed after decapitation, however they were markedly slower. The PsPIN1 auxin efflux carrier in the inhibited axillary buds of intact plants was localised in a non-polar manner. After exogenous application of cytokinin gradual polarisation of the PsPIN1 protein occurred on the basal pole of polar auxin transport competent cells. Despite the fact that direct auxin application to buds of intact plants led to an increase in PsAUX1 and PsPIN1 expression, the buds remained dormant (non-growing what was accompanied by persistent expression of the dormancy markers PsDRM1 and PsAD1. The results indicate a possible effect of cytokinins on biosynthesis, and/or transport of auxin in axillary buds and they highlight the importance of auxin-cytokinin crosstalk in the regulation of bud outgrowth after breaking of apical dominance.

Antibody-mediated modulation of cytokinins in tobacco: Organ-specific changes in cytokinin homeostasis

Czech Academy of Sciences Publication Activity Database

Gelová, Z.; Hoopen, P.; Novák, Ondřej; Motyka, Václav; Pernisová, M.; Dabravolski, S.; Didi, V.; Tillack, F.; Oklešťková, Jana; Strnad, Miroslav; Hause, B.; Haruštiaková, D.; Conrad, U.; Janda, L.; Hejátko, J.

2018-01-01

Roč. 69, č. 3 (2018), s. 441-454 ISSN 0022-0957 R&D Projects: GA MŠk(CZ) LQ1601; GA MŠk(CZ) LO1204; GA MŠk(CZ) LM2015062; GA ČR(CZ) GA16-14649S Institutional support: RVO:61389030 Keywords : Antibody-mediated modulation * biosynthesis * ckx * cytokinin * homeostasis * organ specificity * tobacco Subject RIV: EF - Botanics OBOR OECD: Plant sciences, botany Impact factor: 5.830, year: 2016

Peptide catalysed prebiotic polymerization of RNA

DEFF Research Database (Denmark)

Wieczorek, Rafal; Luisi, Pier Luigi; Monnard, Pierre-Alain

A short peptide composed of only two amino acid residues, serine and histidine, is here reported to enable oligomerization of RNA monomers. SerHis dipeptide was previously reported to catalyse formation of peptide bonds (Gorlero et al. 2009) as well as possessing broad hydrolytic activities...... – in such environment hydrolysis is thermodynamically favoured over condensation. However, the thermodynamic equilibrium towards condensation can be shifted even in this environment. In this poster we describe a prebiotically plausible system in which the SerHis dipeptide acts as catalyst for the formation of RNA...... oligomers from imidazole derivatives of mononucleotides. The thermodynamic shift towards condensation was achieved using water/ice eutectic phase environment (Monnard and Ziock 2008). To obtain such an environment, a reaction solution is cooled below its freezing point, but above the eutectic point. Under...

Relationship between transpiration and amino acid accumulation in Brassica leaf discs treated with cytokinins and fusicoccin

International Nuclear Information System (INIS)

Kuraishi, Susumu; Ishikawa, Fumio

1977-01-01

Both cytokinins and fusicoccin (FC) stimulated the transpiration and the amino acid accumulation in leaf discs of Brassica campestris var. komatsuna. Enhancement effects were of the same magnitude. Both the accumulation and the transpiration were similarly inhibited when vaseline was smeared on the leaf surface. Abscisic acid (ABA) also inhibited those cytokinin-induced effects. The accumulation of amino acid- 14 C was at the cytokinin- or FC-treated site unless the leaf surface was smeared with vaseline. These facts suggest that cytokinin- or FC-induced amino acid accumulation in leaf is caused by the stimulation of transpiration. (auth.)

Rotational barriers of 1,3-substitute pyridines and benzenes as models for the NAD+/NADH coenzyme

NARCIS (Netherlands)

Vanhommerig, S.A.M.; Meier, R.J.; Sluyterman, L.A.A.E.; Meijer, E.M.

1994-01-01

The NAD+/NADH coenzyme is involved in many enzyme-catalysed oxidation-reduction reactions. In order to obtain better insight in the catalytic mechanism of NAD+/NADH dependent dehydrogenases, conformational studies of 1,3-substituted pyridines and benzenes were carried out, using ab initio,

Multicomponent Synthesis of Isoindolinone Frameworks via RhIII -Catalysed in situ Directing Group-Assisted Tandem Oxidative Olefination/Michael Addition.

Science.gov (United States)

Wang, Liang; Liu, Xi; Liu, Jian-Biao; Shen, Jun; Chen, Qun; He, Ming-Yang

2018-04-04

A Rh III -catalysed three-component synthesis of isoindolinone frameworks via direct assembly of benzoyl chlorides, o-aminophenols and activated alkenes has been developed. The process involves in situ generation of o-aminophenol (OAP)-based bidentate directing group (DG), Rh III -catalysed tandem ortho C-H olefination and subsequent cyclization via aza-Michael addition. This protocol exhibits good chemoselectivity and functional group tolerance. Computational studies showed that the presence of hydroxyl group on the N-aryl ring could enhance the chemoselectivity of the reaction. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Transcriptome of the inflorescence meristems of the biofuel plant Jatropha curcas treated with cytokinin.

Science.gov (United States)

Pan, Bang-Zhen; Chen, Mao-Sheng; Ni, Jun; Xu, Zeng-Fu

2014-11-17

Jatropha curcas, whose seed content is approximately 30-40% oil, is an ideal feedstock for producing biodiesel and bio-jet fuels. However, Jatropha plants have a low number of female flowers, which results in low seed yield that cannot meet the needs of the biofuel industry. Thus, increasing the number of female flowers is critical for the improvement of Jatropha seed yield. Our previous findings showed that cytokinin treatment can increase the flower number and female to male ratio and also induce bisexual flowers in Jatropha. The mechanisms underlying the influence of cytokinin on Jatropha flower development and sex determination, however, have not been clarified. This study examined the transcriptional levels of genes involved in the response to cytokinin in Jatropha inflorescence meristems at different time points after cytokinin treatment by 454 sequencing, which gave rise to a total of 294.6 Mb of transcript sequences. Up-regulated and down-regulated annotated and novel genes were identified, and the expression levels of the genes of interest were confirmed by qRT-PCR. The identified transcripts include those encoding genes involved in the biosynthesis, metabolism, and signaling of cytokinin and other plant hormones, flower development and cell division, which may be related to phenotypic changes of Jatropha in response to cytokinin treatment. Our analysis indicated that Jatropha orthologs of the floral organ identity genes known as ABCE model genes, JcAP1,2, JcPI, JcAG, and JcSEP1,2,3, were all significantly repressed, with an exception of one B-function gene JcAP3 that was shown to be up-regulated by BA treatment, indicating different mechanisms to be involved in the floral organ development of unisexual flowers of Jatropha and bisexual flowers of Arabidopsis. Several cell division-related genes, including JcCycA3;2, JcCycD3;1, JcCycD3;2 and JcTSO1, were up-regulated, which may contribute to the increased flower number after cytokinin treatment. This study

The Cytokinin Requirement for Cell Division in Cultured Nicotiana plumbaginifolia Cells Can Be Satisfied by Yeast Cdc25 Protein Tyrosine Phosphatase. Implications for Mechanisms of Cytokinin Response and Plant Development

Science.gov (United States)

Zhang, Kerong; Diederich, Ludger; John, Peter C.L.

2005-01-01

Cultured cells of Nicotiana plumbaginifolia, when deprived of exogenous cytokinin, arrest in G2 phase prior to mitosis and then contain cyclin-dependent protein kinase (CDK) that is inactive because phosphorylated on tyrosine (Tyr). The action of cytokinin in stimulating the activation of CDK by removal of inhibitory phosphorylation from Tyr is not a secondary downstream consequence of other hormone actions but is the key primary effect of the hormone in its stimulation of cell proliferation, since cytokinin could be replaced by expression of cdc25, which encodes the main Cdc2 (CDK)-Tyr dephosphorylating enzyme of yeast (Saccharomyces cerevisiae). The cdc25 gene, under control of a steroid-inducible promoter, induced a rise in cdc25 mRNA, accumulation of p67Cdc25 protein, and increase in Cdc25 phosphatase activity that was measured in vitro with Tyr-phosphorylated Cdc2 as substrate. Cdc25 phosphatase activity peaked during mitotic prophase at the time CDK activation was most rapid. Mitosis that was induced by cytokinin also involved increase in endogenous plant CDK Tyr phosphatase activity during prophase, therefore indicating that this is a normal part of plant mitosis. These results suggest a biochemical mechanism for several previously described transgene phenotypes in whole plants and suggest that a primary signal from cytokinin leading to progression through mitosis is the activation of CDK by dephosphorylation of Tyr. PMID:15618425

The cytokinin requirement for cell division in cultured Nicotiana plumbaginifolia cells can be satisfied by yeast Cdc25 protein tyrosine phosphatase: implications for mechanisms of cytokinin response and plant development.

Science.gov (United States)

Zhang, Kerong; Diederich, Ludger; John, Peter C L

2005-01-01

Cultured cells of Nicotiana plumbaginifolia, when deprived of exogenous cytokinin, arrest in G2 phase prior to mitosis and then contain cyclin-dependent protein kinase (CDK) that is inactive because phosphorylated on tyrosine (Tyr). The action of cytokinin in stimulating the activation of CDK by removal of inhibitory phosphorylation from Tyr is not a secondary downstream consequence of other hormone actions but is the key primary effect of the hormone in its stimulation of cell proliferation, since cytokinin could be replaced by expression of cdc25, which encodes the main Cdc2 (CDK)-Tyr dephosphorylating enzyme of yeast (Saccharomyces cerevisiae). The cdc25 gene, under control of a steroid-inducible promoter, induced a rise in cdc25 mRNA, accumulation of p67(Cdc25) protein, and increase in Cdc25 phosphatase activity that was measured in vitro with Tyr-phosphorylated Cdc2 as substrate. Cdc25 phosphatase activity peaked during mitotic prophase at the time CDK activation was most rapid. Mitosis that was induced by cytokinin also involved increase in endogenous plant CDK Tyr phosphatase activity during prophase, therefore indicating that this is a normal part of plant mitosis. These results suggest a biochemical mechanism for several previously described transgene phenotypes in whole plants and suggest that a primary signal from cytokinin leading to progression through mitosis is the activation of CDK by dephosphorylation of Tyr.

Reactivation of meristem activity and sprout growth in potato tubers require both cytokinin and gibberellin.

Science.gov (United States)

Hartmann, Anja; Senning, Melanie; Hedden, Peter; Sonnewald, Uwe; Sonnewald, Sophia

2011-02-01

Reactivation of dormant meristems is of central importance for plant fitness and survival. Due to their large meristem size, potato (Solanum tuberosum) tubers serve as a model system to study the underlying molecular processes. The phytohormones cytokinins (CK) and gibberellins (GA) play important roles in releasing potato tuber dormancy and promoting sprouting, but their mode of action in these processes is still obscure. Here, we established an in vitro assay using excised tuber buds to study the dormancy-releasing capacity of GA and CK and show that application of gibberellic acid (GA(3)) is sufficient to induce sprouting. In contrast, treatment with 6-benzylaminopurine induced bud break but did not support further sprout growth unless GA(3) was administered additionally. Transgenic potato plants expressing Arabidopsis (Arabidopsis thaliana) GA 20-oxidase or GA 2-oxidase to modify endogenous GA levels showed the expected phenotypical changes as well as slight effects on tuber sprouting. The isopentenyltransferase (IPT) from Agrobacterium tumefaciens and the Arabidopsis cytokinin oxidase/dehydrogenase1 (CKX) were exploited to modify the amounts of CK in transgenic potato plants. IPT expression promoted earlier sprouting in vitro. Strikingly, CKX-expressing tubers exhibited a prolonged dormancy period and did not respond to GA(3). This supports an essential role of CK in terminating tuber dormancy and indicates that GA is not sufficient to break dormancy in the absence of CK. GA(3)-treated wild-type and CKX-expressing tuber buds were subjected to a transcriptome analysis that revealed transcriptional changes in several functional groups, including cell wall metabolism, cell cycle, and auxin and ethylene signaling, denoting events associated with the reactivation of dormant meristems.

Fiber-Optic Bio-sniffer (Biochemical Gas Sensor) Using Reverse Reaction of Alcohol Dehydrogenase for Exhaled Acetaldehyde.

Science.gov (United States)

Iitani, Kenta; Chien, Po-Jen; Suzuki, Takuma; Toma, Koji; Arakawa, Takahiro; Iwasaki, Yasuhiko; Mitsubayashi, Kohji

2018-02-23

Volatile organic compounds (VOCs) exhaled in breath have huge potential as indicators of diseases and metabolisms. Application of breath analysis for disease screening and metabolism assessment is expected since breath samples can be noninvasively collected and measured. In this research, a highly sensitive and selective biochemical gas sensor (bio-sniffer) for gaseous acetaldehyde (AcH) was developed. In the AcH bio-sniffer, a reverse reaction of alcohol dehydrogenase (ADH) was employed for reducing AcH to ethanol and simultaneously consuming a coenzyme, reduced form of nicotinamide adenine dinucleotide (NADH). The concentration of AcH can be quantified by fluorescence detection of NADH that was consumed by reverse reaction of ADH. The AcH bio-sniffer was composed of an ultraviolet light-emitting diode (UV-LED) as an excitation light source, a photomultiplier tube (PMT) as a fluorescence detector, and an optical fiber probe, and these three components were connected with a bifurcated optical fiber. A gas-sensing region of the fiber probe was developed with a flow-cell and an ADH-immobilized membrane. In the experiment, after optimization of the enzyme reaction conditions, the selectivity and dynamic range of the AcH bio-sniffer were investigated. The AcH bio-sniffer showed a short measurement time (within 2 min) and a broad dynamic range for determination of gaseous AcH, 0.02-10 ppm, which encompassed a typical AcH concentration in exhaled breath (1.2-6.0 ppm). Also, the AcH bio-sniffer exhibited a high selectivity to gaseous AcH based on the specificity of ADH. The sensor outputs were observed only from AcH-contained standard gaseous samples. Finally, the AcH bio-sniffer was applied to measure the concentration of AcH in exhaled breath from healthy subjects after ingestion of alcohol. As a result, a significant difference of AcH concentration between subjects with different aldehyde dehydrogenase type 2 (ALDH2) phenotypes was observed. The AcH bio-sniffer can be

Gold film-catalysed benzannulation by Microwave-Assisted, Continuous Flow Organic Synthesis (MACOS

Directory of Open Access Journals (Sweden)

Gjergji Shore

2009-07-01

Full Text Available Methodology has been developed for laying down a thin gold-on-silver film on the inner surface of glass capillaries for the purpose of catalysing benzannulation reactions. The cycloaddition precursors are flowed through these capillaries while the metal film is being heated to high temperatures using microwave irradiation. The transformation can be optimized rapidly, tolerates a wide number of functional groups, is highly regioselective, and proceeds in good to excellent conversion.

Isotopic labelling studies for a gold-catalysed skeletal rearrangement of alkynyl aziridines

Directory of Open Access Journals (Sweden)

Neil Spencer

2011-06-01

Full Text Available Isotopic labelling studies were performed to probe a proposed 1,2-aryl shift in the gold-catalysed cycloisomerisation of alkynyl aziridines into 2,4-disubstituted pyrroles. Two isotopomers of the expected skeletal rearrangement product were identified using 13C-labelling and led to a revised mechanism featuring two distinct skeletal rearrangements. The mechanistic proposal has been rationalised against the reaction of a range of 13C- and deuterium-labelled substrates.

Kinetics of bromide catalysed oxidation of dextrose by cerium (IV) in aqueous sulphuric acid solution

International Nuclear Information System (INIS)

Sharma, J.; Sah, M.P.

1994-01-01

Kinetics of bromide catalysed oxidation of dextrose by Ce IV in aqueous sulphuric acid medium show first order dependence each in dextrose and cerium(IV). The reaction rate decreases on increasing the concentration of hydrogen ion. The increase in [HSO 4 - ] or [SO 4 2- ] decreases the rate. The bromide ion shows positive catalytic effect on the reaction rate. The value of activation energy has been calculated and a suitable mechanism confirming to the kinetic data is proposed. (author). 3 refs., 3 tabs

A parasitic nematode releases cytokinin that controls cell division and orchestrates feeding site formation in host plants.

Science.gov (United States)

Siddique, Shahid; Radakovic, Zoran S; De La Torre, Carola M; Chronis, Demosthenis; Novák, Ondřej; Ramireddy, Eswarayya; Holbein, Julia; Matera, Christiane; Hütten, Marion; Gutbrod, Philipp; Anjam, Muhammad Shahzad; Rozanska, Elzbieta; Habash, Samer; Elashry, Abdelnaser; Sobczak, Miroslaw; Kakimoto, Tatsuo; Strnad, Miroslav; Schmülling, Thomas; Mitchum, Melissa G; Grundler, Florian M W

2015-10-13

Sedentary plant-parasitic cyst nematodes are biotrophs that cause significant losses in agriculture. Parasitism is based on modifications of host root cells that lead to the formation of a hypermetabolic feeding site (a syncytium) from which nematodes withdraw nutrients. The host cell cycle is activated in an initial cell selected by the nematode for feeding, followed by activation of neighboring cells and subsequent expansion of feeding site through fusion of hundreds of cells. It is generally assumed that nematodes manipulate production and signaling of the plant hormone cytokinin to activate cell division. In fact, nematodes have been shown to produce cytokinin in vitro; however, whether the hormone is secreted into host plants and plays a role in parasitism remained unknown. Here, we analyzed the spatiotemporal activation of cytokinin signaling during interaction between the cyst nematode, Heterodera schachtii, and Arabidopsis using cytokinin-responsive promoter:reporter lines. Our results showed that cytokinin signaling is activated not only in the syncytium but also in neighboring cells to be incorporated into syncytium. An analysis of nematode infection on mutants that are deficient in cytokinin or cytokinin signaling revealed a significant decrease in susceptibility of these plants to nematodes. Further, we identified a cytokinin-synthesizing isopentenyltransferase gene in H. schachtii and show that silencing of this gene in nematodes leads to a significant decrease in virulence due to a reduced expansion of feeding sites. Our findings demonstrate the ability of a plant-parasitic nematode to synthesize a functional plant hormone to manipulate the host system and establish a long-term parasitic interaction.

Light Controls Cytokinin Signaling via Transcriptional Regulation of Constitutively Active Sensor Histidine Kinase CKI1.

Science.gov (United States)

Dobisova, Tereza; Hrdinova, Vendula; Cuesta, Candela; Michlickova, Sarka; Urbankova, Ivana; Hejatkova, Romana; Zadnikova, Petra; Pernisova, Marketa; Benkova, Eva; Hejatko, Jan

2017-05-01

In plants, the multistep phosphorelay (MSP) pathway mediates a range of regulatory processes, including those activated by cytokinins. The cross talk between cytokinin response and light has been known for a long time. However, the molecular mechanism underlying the interaction between light and cytokinin signaling remains elusive. In the screen for upstream regulators we identified a LONG PALE HYPOCOTYL ( LPH ) gene whose activity is indispensable for spatiotemporally correct expression of CYTOKININ INDEPENDENT1 ( CKI1 ), encoding the constitutively active sensor His kinase that activates MSP signaling. lph is a new allele of HEME OXYGENASE1 ( HY1 ) that encodes the key protein in the biosynthesis of phytochromobilin, a cofactor of photoconvertible phytochromes. Our analysis confirmed the light-dependent regulation of the CKI1 expression pattern. We show that CKI1 expression is under the control of phytochrome A (phyA), functioning as a dual (both positive and negative) regulator of CKI1 expression, presumably via the phyA-regulated transcription factors (TF) PHYTOCHROME INTERACTING FACTOR3 and CIRCADIAN CLOCK ASSOCIATED1. Changes in CKI1 expression observed in lph / hy1 - 7 and phy mutants correlate with misregulation of MSP signaling, changed cytokinin sensitivity, and developmental aberrations that were previously shown to be associated with cytokinin and/or CKI1 action. Besides that, we demonstrate a novel role of phyA-dependent CKI1 expression in the hypocotyl elongation and hook development during skotomorphogenesis. Based on these results, we propose that the light-dependent regulation of CKI1 provides a plausible mechanistic link underlying the well-known interaction between light- and cytokinin-controlled plant development. © 2017 American Society of Plant Biologists. All Rights Reserved.

Cytokinin signaling regulates cambial development in poplar

Czech Academy of Sciences Publication Activity Database

Nieminen, K.; Immanen, J.; Laxell, M.; Kauppinen, L.; Tarkowski, Petr; Doležal, Karel; Tähtiharju, S.; Elo, A.; Decourteix, M.; Ljung, K.; Bhalerao, R.; Keinonen, K.; Albert, V. A.; Helariutta, Y.

2008-01-01

Roč. 105, č. 50 (2008), s. 20032-20037 ISSN 0027-8424 Institutional research plan: CEZ:AV0Z50380511 Keywords : cambial activity * cambium * secondary development * Populus * CYTOKININ OXIDASE Subject RIV: CE - Biochemistry Impact factor: 9.380, year: 2008

Aromatic cytokinins in micropropagated potato plants

Czech Academy of Sciences Publication Activity Database

Baroja, F. E.; Aguirreolea, J.; Martínková, Hana; Hanuš, Jan; Strnad, Miroslav

2002-01-01

Roč. 40, č. 3 (2002), s. 217-224 ISSN 0981-9428 R&D Projects: GA MŠk OC 844.10; GA ČR GA301/02/0475 Institutional research plan: CEZ:AV0Z5038910 Keywords : Acclimatization * Aromatic cytokinins * Micropropagation Subject RIV: CE - Biochemistry Impact factor: 1.582, year: 2002

Overexpression, crystallization and preliminary X-ray crystallographic analysis of erythronate-4-phosphate dehydrogenase from Pseudomonas aeruginosa.

Science.gov (United States)

Ha, Jun Yong; Lee, Ji Hyun; Kim, Kyoung Hoon; Kim, Do Jin; Lee, Hyung Ho; Kim, Hye-Kyung; Yoon, Hye-Jin; Suh, Se Won

2006-02-01

The enzyme erythronate-4-phosphate dehydrogenase catalyses the conversion of erythronate-4-phosphate to 3-hydroxy-4-phospho-hydroxy-alpha-ketobutyrate. It belongs to the D-isomer-specific 2-hydroxyacid dehydrogenase family. It is essential for de novo biosynthesis of vitamin B6 (pyridoxine). Erythronate-4-phosphate dehydrogenase from Pseudomonas aeruginosa, a homodimeric enzyme consisting of two identical 380-residue subunits, has been overexpressed in Escherichia coli with a C-terminal purification tag and crystallized at 297 K using 0.7 M ammonium dihydrogen phosphate, 0.4 M ammonium tartrate, 0.1 M sodium citrate pH 5.6 and 10 mM cupric chloride. X-ray diffraction data were collected to 2.20 A from a crystal grown in the presence of NADH. The crystals belong to the orthorhombic space group P2(1)2(1)2(1), with unit-cell parameters a = 84.77, b = 101.28, c = 142.58 A. A dimeric molecule is present in the asymmetric unit, giving a crystal volume per protein weight (VM) of 3.64 A3 Da(-1) and a solvent content of 66%.

The influence of growth retardants and cytokinins on flowering of ornamental plants

Directory of Open Access Journals (Sweden)

Anna Pobudkiewicz

2012-12-01

Full Text Available Growth retardants are applied in order to obtain short and well compact plants. They usually inhibit stem elongation, but also can influence the flowering of plants. The aim of cytokinin application is to obtain well branched plants without removing the apical meristem. Cytokinins usually increase the number of axillary shoots but also can influence flowering. Growth retardants and cytokinins can affect flower size, pedicel length, number of flowers, flower longevity, abortion of flower buds and number of days from potting plants to the first open flower. Flowering of growth retardant and cytokinin treated plants might depend on the method of growth regulator used (foliar spray or soil drench, plant species or even a plant cultivar, but in the highest degree it depends on the growth regulator rate used. These growth regulators, when are applied at rates appropriate for height and habit control, very seldom influence flowering of ornamental plants, but applied at high rates can delay flowering, diminish flower diameter or flower pedicel length and also can decrease the number of flowers per plant. In cultivation of bulb plants, growth retardants, used at very high rates, also cause abortion of flower buds.

Kinetic studies of the acylation of pig muscle–d-glyceraldehyde 3-phosphate dehydrogenase by 1,3-diphosphoglycerate and of proton uptake and release in the overall enzyme mechanism

Science.gov (United States)

Harrigan, P. J.; Trentham, D. R.

1973-01-01

In the presence of NAD+ the acylation by 1,3-diphosphoglycerate of the four active sites of pig muscle d-glyceraldehyde 3-phosphate dehydrogenase can be monitored at 365nm by the disappearance of the absorption band present in the binary complex of NAD+ and the enzyme. A non-specific salt effect decreased the acylation rate 25-fold when the ionic strength was increased from 0.10 to 1.0. This caused acylation to be the rate-limiting process in the enzyme-catalysed reductive dephosphorylation of 1,3-diphosphoglycerate at high ionic strength at pH8. The salt effect permitted investigation of the acylation over a wide range of conditions. Variation of pH from 5.4 to 8.6 produced at most a two-fold change in the acylation rate. One proton was taken up per site acylated at pH8.0. By using a chromophoric H+ indicator the rate of proton uptake could be monitored during the acylation and was also almost invariant in the pH range 5.5–8.5. Transient kinetic studies of the overall enzyme-catalysed reaction indicated that acylation was the process involving proton uptake at pH8.0. The enzyme mechanism is discussed in the light of these results. PMID:4360248

N-Heterocyclic Carbene-Catalysed Diastereoselective Vinylogous Michael Addition Reaction of gamma-Substituted deconjugated Butenolides

KAUST Repository

Guo, Hao

2015-11-16

An efficient N-heterocyclic carbene (NHC)-catalysed vinylogous Michael addition of deconjugated butenolides was developed. In the presence of 5 mol% of the NHC catalyst, both γ-alkyl and aryl-substituted deconjugated butenolides undergo vinylogous Michael addition with various α, β-unsaturated ketones, esters, or nitriles to afford γ,γ-disubstituted butenolides containing adjacent quaternary and tertiary carbon centers in good to excellent yields with excellent diastereoselectivities. In this process, the free carbene is assumed to act as a strong Brønsted base to promote the conjugate addition.

N-Heterocyclic Carbene-Catalysed Diastereoselective Vinylogous Michael Addition Reaction of gamma-Substituted deconjugated Butenolides

KAUST Repository

Guo, Hao; Xing, Fen; Du, Guang-Fen; Huang, Kuo-Wei; Dai, Bin; He, Lin

2015-01-01

An efficient N-heterocyclic carbene (NHC)-catalysed vinylogous Michael addition of deconjugated butenolides was developed. In the presence of 5 mol% of the NHC catalyst, both γ-alkyl and aryl-substituted deconjugated butenolides undergo vinylogous Michael addition with various α, β-unsaturated ketones, esters, or nitriles to afford γ,γ-disubstituted butenolides containing adjacent quaternary and tertiary carbon centers in good to excellent yields with excellent diastereoselectivities. In this process, the free carbene is assumed to act as a strong Brønsted base to promote the conjugate addition.

Two genes with similarity to bacterial response regulators are rapidly and specifically induced by cytokinin in Arabidopsis

Science.gov (United States)

Brandstatter, I.; Kieber, J. J.; Evans, M. L. (Principal Investigator)

1998-01-01

Cytokinins are central regulators of plant growth and development, but little is known about their mode of action. By using differential display, we identified a gene, IBC6 (for induced by cytokinin), from etiolated Arabidopsis seedlings, that is induced rapidly by cytokinin. The steady state level of IBC6 mRNA was elevated within 10 min by the exogenous application of cytokinin, and this induction did not require de novo protein synthesis. IBC6 was not induced by other plant hormones or by light. A second Arabidopsis gene with a sequence highly similar to IBC6 was identified. This IBC7 gene also was induced by cytokinin, although with somewhat slower kinetics and to a lesser extent. The pattern of expression of the two genes was similar, with higher expression in leaves, rachises, and flowers and lower transcript levels in roots and siliques. Sequence analysis revealed that IBC6 and IBC7 are similar to the receiver domain of bacterial two-component response regulators. This homology, coupled with previously published work on the CKI1 histidine kinase homolog, suggests that these proteins may play a role in early cytokinin signaling.

Endogenous isoprenoid and aromatic cytokinins in different plant parts of Cocos nucifera (L.)

Czech Academy of Sciences Publication Activity Database

Sáenz, L.; Jones, L. H.; Oropeza, C.; Vláčil, D.; Strnad, Miroslav

2003-01-01

Roč. 39, č. 3 (2003), s. 205-215 ISSN 0167-6903 Grant - others:Centro de Investigación(MX) 88207; Volkswagen Stiftung(DE) I/76 865 Institutional research plan: CEZ:AV0Z5038910; CEZ:MSM 153100008 Keywords : Cocos nucifera * Cytokinin identification * Cytokinin quantification Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 0.688, year: 2003

Overexpression, crystallization and preliminary X-ray crystallographic analysis of erythronate-4-phosphate dehydrogenase from Pseudomonas aeruginosa

Energy Technology Data Exchange (ETDEWEB)

Ha, Jun Yong; Lee, Ji Hyun; Kim, Kyoung Hoon; Kim, Do Jin; Lee, Hyung Ho; Kim, Hye-Kyung; Yoon, Hye-Jin; Suh, Se Won, E-mail: sewonsuh@snu.ac.kr [Department of Chemistry, College of Natural Sciences, Seoul National University, Seoul 151-742 (Korea, Republic of)

2006-02-01

Erythronate-4-phosphate dehydrogenase from P. aeruginosa was crystallized and X-ray diffraction data were collected to 2.20 Å resolution. The enzyme erythronate-4-phosphate dehydrogenase catalyses the conversion of erythronate-4-phosphate to 3-hydroxy-4-phospho-hydroxy-α-ketobutyrate. It belongs to the d-isomer-specific 2-hydroxyacid dehydrogenase family. It is essential for de novo biosynthesis of vitamin B{sub 6} (pyridoxine). Erythronate-4-phosphate dehydrogenase from Pseudomonas aeruginosa, a homodimeric enzyme consisting of two identical 380-residue subunits, has been overexpressed in Escherichia coli with a C-terminal purification tag and crystallized at 297 K using 0.7 M ammonium dihydrogen phosphate, 0.4 M ammonium tartrate, 0.1 M sodium citrate pH 5.6 and 10 mM cupric chloride. X-ray diffraction data were collected to 2.20 Å from a crystal grown in the presence of NADH. The crystals belong to the orthorhombic space group P2{sub 1}2{sub 1}2{sub 1}, with unit-cell parameters a = 84.77, b = 101.28, c = 142.58 Å. A dimeric molecule is present in the asymmetric unit, giving a crystal volume per protein weight (V{sub M}) of 3.64 Å{sup 3} Da{sup −1} and a solvent content of 66%.

Overexpression, crystallization and preliminary X-ray crystallographic analysis of erythronate-4-phosphate dehydrogenase from Pseudomonas aeruginosa

International Nuclear Information System (INIS)

Ha, Jun Yong; Lee, Ji Hyun; Kim, Kyoung Hoon; Kim, Do Jin; Lee, Hyung Ho; Kim, Hye-Kyung; Yoon, Hye-Jin; Suh, Se Won

2006-01-01

Erythronate-4-phosphate dehydrogenase from P. aeruginosa was crystallized and X-ray diffraction data were collected to 2.20 Å resolution. The enzyme erythronate-4-phosphate dehydrogenase catalyses the conversion of erythronate-4-phosphate to 3-hydroxy-4-phospho-hydroxy-α-ketobutyrate. It belongs to the d-isomer-specific 2-hydroxyacid dehydrogenase family. It is essential for de novo biosynthesis of vitamin B 6 (pyridoxine). Erythronate-4-phosphate dehydrogenase from Pseudomonas aeruginosa, a homodimeric enzyme consisting of two identical 380-residue subunits, has been overexpressed in Escherichia coli with a C-terminal purification tag and crystallized at 297 K using 0.7 M ammonium dihydrogen phosphate, 0.4 M ammonium tartrate, 0.1 M sodium citrate pH 5.6 and 10 mM cupric chloride. X-ray diffraction data were collected to 2.20 Å from a crystal grown in the presence of NADH. The crystals belong to the orthorhombic space group P2 1 2 1 2 1 , with unit-cell parameters a = 84.77, b = 101.28, c = 142.58 Å. A dimeric molecule is present in the asymmetric unit, giving a crystal volume per protein weight (V M ) of 3.64 Å 3 Da −1 and a solvent content of 66%

Identification, Cloning, and Characterization of l-Phenylserine Dehydrogenase from Pseudomonas syringae NK-15

Directory of Open Access Journals (Sweden)

Sakuko Ueshima

2010-01-01

Full Text Available The gene encoding d-phenylserine dehydrogenase from Pseudomonas syringae NK-15 was identified, and a 9,246-bp nucleotide sequence containing the gene was sequenced. Six ORFs were confirmed in the sequenced region, four of which were predicted to form an operon. A homology search of each ORF predicted that orf3 encoded l-phenylserine dehydrogenase. Hence, orf3 was cloned and overexpressed in Escherichia coli cells and recombinant ORF3 was purified to homogeneity and characterized. The purified ORF3 enzyme showed l-phenylserine dehydrogenase activity. The enzymological properties and primary structure of l-phenylserine dehydrogenase (ORF3 were quite different from those of d-phenylserine dehydrogenase previously reported. l-Phenylserine dehydrogenase catalyzed the NAD+-dependent oxidation of the β-hydroxyl group of l-β-phenylserine. l-Phenylserine and l-threo-(2-thienylserine were good substrates for l-phenylserine dehydrogenase. The genes encoding l-phenylserine dehydrogenase and d-phenylserine dehydrogenase, which is induced by phenylserine, are located in a single operon. The reaction products of both enzymatic reactions were 2-aminoacetophenone and CO2.

Kinetics of acyl transfer reactions in organic media catalysed by Candida antarctica lipase B.

Science.gov (United States)

Martinelle, M; Hult, K

1995-09-06

The acyl transfer reactions catalysed by Candida antartica lipase B in organic media followed a bi-bi ping-pong mechanism, with competitive substrate inhibition by the alcohols used as acyl acceptors. The effect of organic solvents on Vm and Km was investigated. The Vm values in acetonitrile was 40-50% of those in heptane. High Km values in acetonitrile compared to those in heptane could partly be explained by an increased solvation of the substrates in acetonitrile. Substrate solvation caused a 10-fold change in substrate specificity, defined as (Vm/Km)ethyl octanoate/(Vm/Km)octanoic acid, going from heptane to acetonitrile. Deacylation was the rate determining step for the acyl transfer in heptane with vinyl- and ethyl octanoate as acyl donors and (R)-2-octanol as acyl acceptor. With 1-octanol, a rate determining deacylation step in heptane was indicated using the same acyl donors. Using 1-octanol as acceptor in heptane, S-ethyl thiooctanoate had a 25- to 30-fold lower Vm/Km value and vinyl octanoate a 4-fold higher Vm/Km value than that for ethyl octanoate. The difference showed to be a Km effect for vinyl octanoate and mainly a Km effect for S-ethyl thiooctanoate. The Vm values of the esterification of octanoic acid with different alcohols was 10-30-times lower than those for the corresponding transesterification of ethyl octanoate. The low activity could be explained by a low pH around the enzyme caused by the acid or a withdrawing of active enzyme by nonproductive binding by the acid.

Production of uranium hexafluoride by the catalysed fluorox process: pilot plant and supporting bench-scale studies

International Nuclear Information System (INIS)

Janov, J.; Charlton, B.G.; LePage, A.H.; Vilkaitis, V.K.

1982-04-01

The feasibility of producing UF 6 by the catalysed reaction of UF 4 with oxygen (the Fluorox process) was investigated in a 150 mm diameter fluidised bed reactor and in supporting bench-scale experiments. The rate of the Fluorox reaction in batch experiments was increased by an order of magnitude with 1 to 5 per cent catalyst (containing 3 to 4 per cent platinum on alumina). The maximum UF 6 production rate at 650 deg. C was 0.9 kg h -1 . However, the platinum catalyst was completely poisoned after production of only 1 and 20 kg UF 6 per kg of catalyst when using respectively French and British UF 4 . Regeneration of the catalyst was demonstrated to be technically feasible by washing with water or ammonium oxalate solution or treating with hydrogen and hydrogen fluoride at 350-650 deg. C. However, since the very fast rate of poisoning would necessitate higher catalyst concentrations and/or frequent regeneration, the catalysed Fluorox process in unlikely to be economically competitive with the direct fluorination of UF 4

Proteasomal control of cytokinin synthesis protects Mycobacterium tuberculosis against nitric oxide

Science.gov (United States)

Samanovic, Marie I.; Tu, Shengjiang; Novák, Ondřej; Iyer, Lakshminarayan M.; McAllister, Fiona E.; Aravind, L.; Gygi, Steven P.; Hubbard, Stevan R.; Strnad, Miroslav; Darwin, K. Heran

2015-01-01

Summary One of several roles of the Mycobacterium tuberculosis proteasome is to defend against host-produced nitric oxide (NO), a free radical that can damage numerous biological macromolecules. Mutations that inactivate proteasomal degradation in Mycobacterium tuberculosis result in bacteria that are hypersensitive to NO and attenuated for growth in vivo, but it was not known why. To elucidate the link between proteasome function, NO-resistance, and pathogenesis, we screened for suppressors of NO hypersensitivity in a mycobacterial proteasome ATPase mutant and identified mutations in Rv1205. We determined that Rv1205 encodes a pupylated proteasome substrate. Rv1205 is a homologue of the plant enzyme LONELY GUY, which catalyzes the production of hormones called cytokinins. Remarkably, we report for the first time that an obligate human pathogen secretes several cytokinins. Finally, we determined that the Rv1205-dependent accumulation of cytokinin breakdown products is likely responsible for the sensitization of Mycobacterium tuberculosis proteasome-associated mutants to NO. PMID:25728768

Evaluating Pt-Ru/C mixtures as ethanol electro-oxidation catalysers

Directory of Open Access Journals (Sweden)

Bibian Alonso Hoyos

2004-09-01

Full Text Available This work studies ethanol electro-catalytic oxidation by cyclic voltametry in sulphuric acid solutions at different temperatures and concetrations, using platinum.rutenium mixtures supported in vitreous carbon as catalysers. The results indicate that ethanol oxidation in theses electrodes is irreversible, has slow kinetics, is controlled by charge transfer and is brought about by a bi-functional reaction mechanism, this being ethanol adsorption on platinum atoms and additional oxidation of specties adsorbed in the presence of platinum and retenium oxides. Experimental results show increased catalytic activity with electrodes, followed by reduced activity for electrodes having a greater quantity of rutenium.

Analysis and protease-catalysed synthesis of sucrose alkanoate regioisomers

DEFF Research Database (Denmark)

Lie, Aleksander

2014-01-01

The aims of the presented research were to develop quantifiable methods for reversed-phase high-performance liquid chromatography analysis of sucrose alkanoate regioisomers and to investigate the activity and regioisomeric distribution in the biocatalytic esterification of sucrose with vinyl laur...... in the reaction mixture appeared to be catalysed by the presence of aluminosilicate molecular sieves in the reaction medium. Mass spectrometry analysis of sucrose laurate product confirmed the molecular mass.......The aims of the presented research were to develop quantifiable methods for reversed-phase high-performance liquid chromatography analysis of sucrose alkanoate regioisomers and to investigate the activity and regioisomeric distribution in the biocatalytic esterification of sucrose with vinyl...... laurate in DMF using serine proteases and a metalloprotease. A broad range of elution strategies for the chromatographic analysis of sucrose alkanoate regioisomers was systematically investigated using design of experiments strategies and statistical and multivariate analysis and modelling. Efficiency...

The role of cytokinins in clubroot disease

Czech Academy of Sciences Publication Activity Database

Malinowski, R.; Novák, Ondřej; Borhan, M.H.; Spíchal, Lukáš; Strnad, Miroslav; Rolfe, S.A.

2016-01-01

Roč. 145, č. 3 (2016), s. 543-557 ISSN 0929-1873 R&D Projects: GA MŠk(CZ) LO1204; GA ČR GA15-22322S Institutional support: RVO:61389030 Keywords : Clubroot * Plasmodiophora brassicae * Cytokinins Subject RIV: CE - Biochemistry Impact factor: 1.478, year: 2016

Reaction mechanism of sterol hydroxylation by steroid C25 dehydrogenase - Homology model, reactivity and isoenzymatic diversity.

Science.gov (United States)

Rugor, Agnieszka; Wójcik-Augustyn, Anna; Niedzialkowska, Ewa; Mordalski, Stefan; Staroń, Jakub; Bojarski, Andrzej; Szaleniec, Maciej

2017-08-01

Steroid C25 dehydrogenase (S25DH) is a molybdenum-containing oxidoreductase isolated from the anaerobic Sterolibacterium denitrificans Chol-1S. S25DH is classified as 'EBDH-like' enzyme (EBDH, ethylbenzene dehydrogenase) and catalyzes the introduction of an OH group to the C25 atom of a sterol aliphatic side-chain. Due to its regioselectivity, S25DH is proposed as a catalyst in production of pharmaceuticals: calcifediol or 25-hydroxycholesterol. The aim of presented research was to obtain structural model of catalytic subunit α and investigate the reaction mechanism of the O 2 -independent tertiary carbon atom activation. Based on homology modeling and theoretical calculations, a S25DH α subunit model was for the first time characterized and compared to other S25DH-like isoforms. The molecular dynamics simulations of the enzyme-substrate complexes revealed two stable binding modes of a substrate, which are stabilized predominantly by van der Waals forces in the hydrophobic substrate channel. However, H-bond interactions involving polar residues with C3=O/C3-OH in the steroid ring appear to be responsible for positioning the substrate. These results may explain the experimental kinetic results which showed that 3-ketosterols are hydroxylated 5-10-fold faster than 3-hydroxysterols. The reaction mechanism was studied using QM:MM and QM-only cluster models. The postulated mechanism involves homolytic CH cleavage by the MoO ligand, giving rise to a radical intermediate with product obtained in an OH rebound process. The hypothesis was supported by kinetic isotopic effect (KIE) experiments involving 25,26,26,26-[ 2 H]-cholesterol (4.5) and the theoretically predicted intrinsic KIE (7.0-7.2). Finally, we have demonstrated that the recombinant S25DH-like isoform catalyzes the same reaction as S25DH. Copyright © 2017 Elsevier Inc. All rights reserved.

An Improved in Vivo Deuterium Labeling Method for Measuring the Biosynthetic Rate of Cytokinins

Directory of Open Access Journals (Sweden)

Petr Tarkowski

2010-12-01

Full Text Available An improved method for determining the relative biosynthetic rate of isoprenoid cytokinins has been developed. A set of 11 relevant isoprenoid cytokinins, including zeatin isomers, was separated by ultra performance liquid chromatography in less than 6 min. The iP-type cytokinins were observed to give rise to a previously-unknown fragment at m/z 69; we suggest that the diagnostic (204-69 transition can be used to monitor the biosynthetic rate of isopentenyladenine. Furthermore, we found that by treating the cytokinin nucleotides with alkaline phosphatase prior to analysis, the sensitivity of the detection process could be increased. In addition, derivatization (propionylation improved the ESI-MS response by increasing the analytes' hydrophobicity. Indeed, the ESI-MS response of propionylated isopentenyladenosine was about 34% higher than that of its underivatized counterpart. Moreover, the response of the derivatized zeatin ribosides was about 75% higher than that of underivatized zeatin ribosides. Finally, we created a web-based calculator (IZOTOP that facilitates MS/MS data processing and offer it freely to the research community.

Mechanistic Investigation of Molybdate-Catalysed Transfer Hydrodeoxygenation

DEFF Research Database (Denmark)

Larsen, Daniel Bo; Petersen, Allan Robertson; Dethlefsen, Johannes Rytter

2016-01-01

The molybdate-catalysed transfer hydrodeoxygenation (HDO) of benzyl alcohol to toluene driven by oxidation of the solvent isopropyl alcohol to acetone has been investigated by using a combination of experimental and computational methods. A Hammett study that compared the relative rates for the t......The molybdate-catalysed transfer hydrodeoxygenation (HDO) of benzyl alcohol to toluene driven by oxidation of the solvent isopropyl alcohol to acetone has been investigated by using a combination of experimental and computational methods. A Hammett study that compared the relative rates...

Interactions between ethylene, abscisic acid and cytokinin during ...

Indian Academy of Sciences (India)

Interactions between ethylene, abscisic acid and cytokinin during germination and seedling establishment in Arabidopsis. VEERAPUTHIRAN SUBBIAH and KARINGU JANARDHAN REDDY. J. Biosci. 35(3), September 2010, 451–459 © Indian Academy of Sciences. Supplementary figure. Supplementary figure 1.

Thermodynamic Calculations for Systems Biocatalysis

DEFF Research Database (Denmark)

Abu, Rohana; Gundersen, Maria T.; Woodley, John M.

2015-01-01

the transamination of a pro-chiral ketone into a chiral amine (interesting in many pharmaceutical applications). Here, the products are often less energetically stable than the reactants, meaning that the reaction may be thermodynamically unfavourable. As in nature, such thermodynamically-challenged reactions can...... on the basis of kinetics. However, many of the most interesting non-natural chemical reactions which could potentially be catalysed by enzymes, are thermodynamically unfavourable and are thus limited by the equilibrium position of the reaction. A good example is the enzyme ω-transaminase, which catalyses...... be altered by coupling with other reactions. For instance, in the case of ω-transaminase, such a coupling could be with alanine dehydrogenase. Herein, the aim of this work is to identify thermodynamic bottlenecks within a multi-enzyme process, using group contribution method to calculate the Gibbs free...

Identification and Expression Analysis of Cytokinin Metabolic Genes in Soybean under Normal and Drought Conditions in Relation to Cytokinin Levels

Czech Academy of Sciences Publication Activity Database

Le, D. T.; Nishiyama, R.; Watanabe, Y.; Vaňková, Radomíra; Tanaka, M.; Seki, M.; Ham, L. H.; Yamaguchi-Shinozaki, K.; Shinozaki, K.; Tran, L. S. P.

2012-01-01

Roč. 7, č. 8 (2012), „e42411″ E-ISSN 1932-6203 Institutional research plan: CEZ:AV0Z50380511 Keywords : ZEATIN-TYPE CYTOKININS * TRANSCRIPTIONAL REGULATORY NETWORKS * TRANSGENIC TOBACCO PLANTS Subject RIV: EB - Genetic s ; Molecular Biology Impact factor: 3.730, year: 2012

INFLUENCE OF SELECTED PHARMACEUTICALS ON ACTIVATED SLUDGE DEHYDROGENASE ACTIVITY

Directory of Open Access Journals (Sweden)

Agnieszka Tomska

2016-06-01

The aim of this work was to evaluate the effect of selected antibiotics - sulfanilamide and erythromycin on activated sludge dehydrogenase activity with use of trifenyltetrazolinum chloride (TTC test. Dehydrogenases activity is an indicator of biochemical activity of microorganisms present in activated sludge or the ability to degrade organic compounds in waste water. TTC test is particularly useful for the regularity of the course of treatment, in which the presence of inhibitors of biochemical reactions and toxic compounds are present. It was observed that the dehydrogenase activity decreases with the increase of a antibiotics concentration. The lowest value of the dehydrogenase activity equal to 32.4 μmol TF / gMLSS obtained at sulfanilamide concentration 150mg / l. For this sample, an inhibition of dehydrogenase activity was 31%.

The rice F-box protein KISS ME DEADLY2 functions as a negative regulator of cytokinin signalling.

Science.gov (United States)

Kim, Hyo Jung; Kieber, Joseph J; Schaller, G Eric

2013-01-01

Cytokinins are plant hormones that play critical roles in growth and development. We recently determined that the transcriptional response to cytokinin of Arabidopsis is modulated by the KISS ME DEADLY (KMD) family of F-box proteins. Here we demonstrate a conserved function for a member of the rice KMD family. Ectopic overexpression of OsKMD2 in Arabidopsis results in decreased cytokinin sensitivity based on a hypocotyl growth response assay, the decrease in sensitivity correlating with a decrease in the levels of the transcriptional regulator AtARR12. Furthermore, OsKMD2 directly interacts with AtARR12 based on yeast two-hybrid and co-immunoprecipitation assays. These results indicate that both monocots and dicots employ a similar KMD-dependent mechanism to regulate the transcriptional response to cytokinin.

Palladium-catalysed arylation of acetoacetate esters to yield 2-arylacetic acid esters

CSIR Research Space (South Africa)

Zeevaart, JG

2004-05-24

Full Text Available , was developed simultaneously by Hart- wig and Buchwald.5 Typically the tert-butyl ester of propionic acid is treated with an aryl halide (bromide or chloride) in the presence of a strong base, palladium and a bulky phosphine ligand or a bulky imidazolinium CO2t... novel palladium- catalysed conditions for the arylation of acetoacetate esters resulting in the formation of 2-arylacetic acid esters. When we attempted the arylation of tert-butyl aceto- acetate 1a with bromobenzene 2a using mild reaction conditions (K3...

Molecular Basis for Converting (2S-Methylsuccinyl-CoA Dehydrogenase into an Oxidase

Directory of Open Access Journals (Sweden)

Simon Burgener

2017-12-01

Full Text Available Although flavoenzymes have been studied in detail, the molecular basis of their dioxygen reactivity is only partially understood. The members of the flavin adenosine dinucleotide (FAD-dependent acyl-CoA dehydrogenase and acyl-CoA oxidase families catalyze similar reactions and share common structural features. However, both enzyme families feature opposing reaction specificities in respect to dioxygen. Dehydrogenases react with electron transfer flavoproteins as terminal electron acceptors and do not show a considerable reactivity with dioxygen, whereas dioxygen serves as a bona fide substrate for oxidases. We recently engineered (2S-methylsuccinyl-CoA dehydrogenase towards oxidase activity by rational mutagenesis. Here we characterized the (2S-methylsuccinyl-CoA dehydrogenase wild-type, as well as the engineered (2S-methylsuccinyl-CoA oxidase, in detail. Using stopped-flow UV-spectroscopy and liquid chromatography-mass spectrometry (LC-MS based assays, we explain the molecular base for dioxygen reactivity in the engineered oxidase and show that the increased oxidase function of the engineered enzyme comes at a decreased dehydrogenase activity. Our findings add to the common notion that an increased activity for a specific substrate is achieved at the expense of reaction promiscuity and provide guidelines for rational engineering efforts of acyl-CoA dehydrogenases and oxidases.

pH-Dependent isotope exchange and hydrogenation catalysed by water-soluble NiRu complexes as functional models for [NiFe]hydrogenases.

Science.gov (United States)

Kure, Bunsho; Matsumoto, Takahiro; Ichikawa, Koji; Fukuzumi, Shunichi; Higuchi, Yoshiki; Yagi, Tatsuhiko; Ogo, Seiji

2008-09-21

The pH-dependent hydrogen isotope exchange reaction between gaseous isotopes and medium isotopes and hydrogenation of the carbonyl compounds have been investigated with water-soluble bis(mu-thiolate)(mu-hydride)NiRu complexes, Ni(II)(mu-SR)(2)(mu-H)Ru(II) {(mu-SR)(2) = N,N'-dimethyl-N,N'-bis(2-mercaptoethyl)-1,3-propanediamine}, as functional models for [NiFe]hydrogenases. In acidic media (at pH 4-6), the mu-H ligand of the Ni(II)(mu-SR)(2)(mu-H)Ru(II) complexes has H(+) properties, and the complexes catalyse the hydrogen isotope exchange reaction between gaseous isotopes and medium isotopes. A mechanism of the hydrogen isotope exchange reaction between gaseous isotopes and medium isotopes through a low-valent Ni(I)(mu-SR)(2)Ru(I) complex is proposed. In contrast, in neutral-basic media (at pH 7-10), the mu-H ligand of the Ni(II)(mu-SR)(2)(mu-H)Ru(II) complexes acts as H(-), and the complexes catalyse the hydrogenation of carbonyl compounds.

Cytokinin-producing, plant growth-promoting rhizobacteria that confer resistance to drought stress in Platycladus orientalis container seedlings.

Science.gov (United States)

Liu, Fangchun; Xing, Shangjun; Ma, Hailin; Du, Zhenyu; Ma, Bingyao

2013-10-01

One of the proposed mechanisms through which plant growth-promoting rhizobacteria (PGPR) enhance plant growth is the production of plant growth regulators, especially cytokinin. However, little information is available regarding cytokinin-producing PGPR inoculation on growth and water stress consistence of forest container seedlings under drought condition. This study determined the effects of Bacillus subtilis on hormone concentration, drought resistance, and plant growth under water-stressed conditions. Although no significant difference was observed under well-watered conditions, leaves of inoculated Platycladus orientalis (oriental thuja) seedlings under drought stress had higher relative water content and leaf water potential compared with those of noninoculated ones. Regardless of water supply levels, the root exudates, namely sugars, amino acids and organic acids, significantly increased because of B. subtilis inoculation. Water stress reduced shoot cytokinins by 39.14 %. However, inoculation decreased this deficit to only 10.22 %. The elevated levels of cytokinins in P. orientalis shoot were associated with higher concentration of abscisic acid (ABA). Stomatal conductance was significantly increased by B. subtilis inoculation in well-watered seedlings. However, the promoting effect of cytokinins on stomatal conductance was hampered, possibly by the combined action of elevated cytokinins and ABA. B. subtilis inoculation increased the shoot dry weight of well-watered and drought seedlings by 34.85 and 19.23 %, as well as the root by 15.445 and 13.99 %, respectively. Consequently, the root/shoot ratio significantly decreased, indicative of the greater benefits of PGPR on shoot growth than root. Thus, inoculation of cytokinin-producing PGPR in container seedlings can alleviate the drought stress and interfere with the suppression of shoot growth, showing a real potential to perform as a drought stress inhibitor in arid environments.

Overexpression, crystallization and preliminary X-­ray crystallographic analysis of erythronate-4-phosphate dehydrogenase from Pseudomonas aeruginosa

Science.gov (United States)

Ha, Jun Yong; Lee, Ji Hyun; Kim, Kyoung Hoon; Kim, Do Jin; Lee, Hyung Ho; Kim, Hye-Kyung; Yoon, Hye-Jin; Suh, Se Won

2006-01-01

The enzyme erythronate-4-phosphate dehydrogenase catalyses the conversion of erythronate-4-phosphate to 3-hydroxy-4-phospho-hydroxy-α-ketobutyrate. It belongs to the d-isomer-specific 2-hydroxyacid dehydrogenase family. It is essential for de novo biosynthesis of vitamin B6 (pyridoxine). Erythronate-4-­phosphate dehydrogenase from Pseudomonas aeruginosa, a homodimeric enzyme consisting of two identical 380-residue subunits, has been overexpressed in Escherichia coli with a C-terminal purification tag and crystallized at 297 K using 0.7 M ammonium dihydrogen phosphate, 0.4 M ammonium tartrate, 0.1 M sodium citrate pH 5.6 and 10 mM cupric chloride. X-ray diffraction data were collected to 2.20 Å from a crystal grown in the presence of NADH. The crystals belong to the orthorhombic space group P212121, with unit-cell parameters a = 84.77, b = 101.28, c = 142.58 Å. A dimeric molecule is present in the asymmetric unit, giving a crystal volume per protein weight (V M) of 3.64 Å3 Da−1 and a solvent content of 66%. PMID:16511285

2-Methylbutyryl-coenzyme A dehydrogenase deficiency

DEFF Research Database (Denmark)

Sass, Jörn Oliver; Ensenauer, Regina; Röschinger, Wulf

2008-01-01

2-Methylbutyryl-CoA dehydrogenase (MBD; coded by the ACADSB gene) catalyzes the step in isoleucine metabolism that corresponds to the isovaleryl-CoA dehydrogenase reaction in the degradation of leucine. Deficiencies of both enzymes may be detected by expanded neonatal screening with tandem...... individuals showed clinical symptoms attributable to MBD deficiency although the defect in isoleucine catabolism was demonstrated both in vivo and in vitro. Several mutations in the ACADSB gene were identified, including a novel one. MBD deficiency may be a harmless metabolic variant although significant...

Characterization of cytokinin signaling and homeostasis gene families in two hardwood tree species: Populus trichocarpa and Prunus persica.

Science.gov (United States)

Immanen, Juha; Nieminen, Kaisa; Duchens Silva, Héctor; Rodríguez Rojas, Fernanda; Meisel, Lee A; Silva, Herman; Albert, Victor A; Hvidsten, Torgeir R; Helariutta, Ykä

2013-12-16

Through the diversity of cytokinin regulated processes, this phytohormone has a profound impact on plant growth and development. Cytokinin signaling is involved in the control of apical and lateral meristem activity, branching pattern of the shoot, and leaf senescence. These processes influence several traits, including the stem diameter, shoot architecture, and perennial life cycle, which define the development of woody plants. To facilitate research about the role of cytokinin in regulation of woody plant development, we have identified genes associated with cytokinin signaling and homeostasis pathways from two hardwood tree species. Taking advantage of the sequenced black cottonwood (Populus trichocarpa) and peach (Prunus persica) genomes, we have compiled a comprehensive list of genes involved in these pathways. We identified genes belonging to the six families of cytokinin oxidases (CKXs), isopentenyl transferases (IPTs), LONELY GUY genes (LOGs), two-component receptors, histidine containing phosphotransmitters (HPts), and response regulators (RRs). All together 85 Populus and 45 Prunus genes were identified, and compared to their Arabidopsis orthologs through phylogenetic analyses. In general, when compared to Arabidopsis, differences in gene family structure were often seen in only one of the two tree species. However, one class of genes associated with cytokinin signal transduction, the CKI1-like family of two-component histidine kinases, was larger in both Populus and Prunus than in Arabidopsis.

Catalysis in the Service of Green Chemistry: Nobel Prize-Winning Palladium-Catalysed Cross-Couplings, Run in Water at Room Temperature: Heck, Suzuki-Miyaura and Negishi reactions carried out in the absence of organic solvents, enabled by micellar catalysis.

Science.gov (United States)

Lipshutz, Bruce H; Taft, Benjamin R; Abela, Alexander R; Ghorai, Subir; Krasovskiy, Arkady; Duplais, Christophe

2012-04-01

Palladium-catalysed cross-couplings, in particular Heck, Suzuki-Miyaura and Negishi reactions developed over three decades ago, are routinely carried out in organic solvents. However, alternative media are currently of considerable interest given an increasing emphasis on making organic processes 'greener'; for example, by minimising organic waste in the form of organic solvents. Water is the obvious leading candidate in this regard. Hence, this review focuses on the application of micellar catalysis, in which a 'designer' surfactant enables these award-winning coupling reactions to be run in water at room temperature.

Endogenous cytokinins in shoots of Aloe polyphylla cultured in vitro in relation to hyperhydricity, exogenous cytokinins and gelling agents

Czech Academy of Sciences Publication Activity Database

Ivanova, M.; Novák, Ondřej; Strnad, Miroslav; van Staden, J.

2006-01-01

Roč. 50, 2-3 (2006), s. 219-230 ISSN 0167-6903 R&D Projects: GA ČR GA301/05/0418 Institutional research plan: CEZ:AV0Z50380511 Source of funding: V - iné verejné zdroje Keywords : Aloe polyphylla * Cytokinins * Gelling agent * Hyperhydricity Subject RIV: CE - Biochemistry Impact factor: 0.903, year: 2006

CHASE domain-containing receptors play an essential role in the cytokinin response of the moss Physcomitrella patens

Czech Academy of Sciences Publication Activity Database

von Schwartzenberg, K.; Lindner, A.C.; Gruhn, N.; Šimura, Jan; Novák, Ondřej; Strnad, Miroslav; Gonneau, M.; Nogue, F.; Heyl, A.

2016-01-01

Roč. 67, č. 3 (2016), s. 667-679 ISSN 0022-0957 R&D Projects: GA MŠk(CZ) LO1204 Institutional support: RVO:61389030 Keywords : cytokinin * Bryophyte * cytokinin receptor Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 5.830, year: 2016

Cytokinin-induced upregulation of cytokinin oxidase activity in tobacco includes changes in enzyme glycosylation and secretion

Czech Academy of Sciences Publication Activity Database

Motyka, Václav; Vaňková, Radomíra; Čapková, Věra; Petrášek, Jan; Kamínek, Miroslav; Schmülling, T.

2003-01-01

Roč. 117, č. 1 (2003), s. 11-21 ISSN 0031-9317 R&D Projects: GA ČR GA522/00/1346; GA ČR GA206/02/0967; GA ČR GA522/99/1130; GA AV ČR IAA6038002 Grant - others:Volkswagen Stiftung(DE) I/72076 Institutional research plan: CEZ:AV0Z5038910 Keywords : cytokinin oxidase * Nicotiana tabacum * N6-benzylaminopurine Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 1.767, year: 2003

Crystallization and preliminary crystallographic analysis of Gre2p, an NADP+-dependent alcohol dehydrogenase from Saccharomyces cerevisiae

International Nuclear Information System (INIS)

Breicha, Klaus; Müller, Marion; Hummel, Werner; Niefind, Karsten

2010-01-01

The alcohol dehydrogenase Gre2p from S. cerevisiae catalyses the stereospecific reduction of a variety of different keto compounds and can therefore be applied as a valuable biocatalyst. The crystallization of the complex of Gre2p with NADP + and its preliminary X-ray analysis are described. Gre2p [Genes de respuesta a estres (stress-response gene)] from Saccharomyces cerevisiae is a monomeric enzyme of 342 amino acids with a molecular weight of 38.1 kDa. The enzyme catalyses both the stereospecific reduction of keto compounds and the oxidation of various hydroxy compounds and alcohols by the simultaneous consumption of the cofactor NADPH and formation of NADP + . Crystals of a Gre2p complex with NADP + were grown using PEG 8000 as a precipitant. They belong to the monoclinic space group P2 1 . The current diffraction resolution is 3.2 Å. In spite of the monomeric nature of Gre2p in solution, packing and self-rotation calculations revealed the existence of two Gre2p protomers per asymmetric unit related by a twofold noncrystallographic axis

Cytokinin treatment and flower quality in Phalaenopsis orchids ...

African Journals Online (AJOL)

We previously documented an N-6-benzyladenine (BA) protocol to increase spike and flower number in Phalaenopsis orchids. To increase options for growers, we tested two additional cytokinins, kinetin (Kin) and 2-iso-pentenyl adenine (2-iP), comparing them with BA. Two key commercial cultivars were used ...

Analysis of cytokinin nucleotides by capillary zone electrophoresis with diode array and mass spectrometric detection in a recombinant enzyme in vitro reaction

Czech Academy of Sciences Publication Activity Database

Béres, Tibor; Gemrotová, Markéta; Tarkowski, P.; Ganzera, M.; Maier, V.; Fridecký, D.; Dessoy, M. A.; Wessjohann, L. A.; Spíchal, Lukáš; Strnad, Miroslav; Doležal, Karel

2012-01-01

Roč. 751, Feb (2012), s. 176-181 ISSN 0003-2670 R&D Projects: GA MŠk(CZ) LC06034 Grant - others:GA MŠk(CZ) ED0007/01/01; GA ČR(CZ) GA522/08/0920 Program:ED; GA Institutional research plan: CEZ:AV0Z50380511 Keywords : Cytokinin nucleotides * Capillary electrophoresis * Isopentenyltransferase Subject RIV: ED - Physiology Impact factor: 4.387, year: 2012

Mutagenic effect of gamma radiation on Arabidopsis thaliana. Effect of low temperature and cytokinin

International Nuclear Information System (INIS)

Pesina, K.

1975-01-01

The effect was studied of low temperature and cytokinin (6-benzyl aminopurine) on sterility and mutation frequency in A r a b i d o ps i s t h a l i a n a irradiatied with gamma radiation. Liquid nitrogen temperature was found to modify the radiation effect in that that it reduced sterility and mutation frequency. Cytokinin applied to seed prior to and after irradiation increased mutation frequency. (L.O.)

The QTL GNP1 Encodes GA20ox1, Which Increases Grain Number and Yield by Increasing Cytokinin Activity in Rice Panicle Meristems.

Science.gov (United States)

Wu, Yuan; Wang, Yun; Mi, Xue-Fei; Shan, Jun-Xiang; Li, Xin-Min; Xu, Jian-Long; Lin, Hong-Xuan

2016-10-01

Cytokinins and gibberellins (GAs) play antagonistic roles in regulating reproductive meristem activity. Cytokinins have positive effects on meristem activity and maintenance. During inflorescence meristem development, cytokinin biosynthesis is activated via a KNOX-mediated pathway. Increased cytokinin activity leads to higher grain number, whereas GAs negatively affect meristem activity. The GA biosynthesis genes GA20oxs are negatively regulated by KNOX proteins. KNOX proteins function as modulators, balancing cytokinin and GA activity in the meristem. However, little is known about the crosstalk among cytokinin and GA regulators together with KNOX proteins and how KNOX-mediated dynamic balancing of hormonal activity functions. Through map-based cloning of QTLs, we cloned a GA biosynthesis gene, Grain Number per Panicle1 (GNP1), which encodes rice GA20ox1. The grain number and yield of NIL-GNP1TQ were significantly higher than those of isogenic control (Lemont). Sequence variations in its promoter region increased the levels of GNP1 transcripts, which were enriched in the apical regions of inflorescence meristems in NIL-GNP1TQ. We propose that cytokinin activity increased due to a KNOX-mediated transcriptional feedback loop resulting from the higher GNP1 transcript levels, in turn leading to increased expression of the GA catabolism genes GA2oxs and reduced GA1 and GA3 accumulation. This rebalancing process increased cytokinin activity, thereby increasing grain number and grain yield in rice. These findings uncover important, novel roles of GAs in rice florescence meristem development and provide new insights into the crosstalk between cytokinin and GA underlying development process.

Urea derivatives on the move: cytokinin-like activity and adventitious rooting enhancement depend on chemical structure.

Science.gov (United States)

Ricci, A; Bertoletti, C

2009-05-01

Urea derivatives are synthetic compounds, some of which have proved to be positive regulators of cell division and differentiation. N-phenyl-N'-(2-chloro-4-pyridyl)urea (forchlorofenuron, CPPU) and N-phenyl-N'-(1,2,3-thiadiazol-5-yl)urea (thidiazuron, TDZ), well known urea cytokinin representatives, are extensively used in in vitro plant morphogenesis studies, as they show cytokinin-like activity often exceeding that of adenine compounds. In recent years, renewed interest in structure-activity relationship studies allowed identification of new urea cytokinins and other urea derivatives that specifically enhance adventitious root formation. In this review, we report the research history of urea derivatives, new insights into their biological activity, and recent progress on their mode of action.

A high effective NADH-ferricyanide dehydrogenase coupled with laccase for NAD(+) regeneration.

Science.gov (United States)

Wang, Jizhong; Yang, Chengli; Chen, Xing; Bao, Bingxin; Zhang, Xuan; Li, Dali; Du, Xingfan; Shi, Ruofu; Yang, Junfang; Zhu, Ronghui

2016-08-01

To find an efficient and cheap system for NAD(+) regeneration A NADH-ferricyanide dehydrogenase was obtained from an isolate of Escherichia coli. Optimal activity of the NADH dehydrogenase was at 45 °C and pH 7.5, with a K m value for NADH of 10 μM. By combining the NADH dehydrogenase, potassium ferricyanide and laccase, a bi-enzyme system for NAD(+) regeneration was established. The system is attractive in that the O2 consumed by laccase is from air and the sole byproduct of the reaction is water. During the reaction process, 10 mM NAD(+) was transformed from NADH in less than 2 h under the condition of 0.5 U NADH dehydrogenase, 0.5 U laccase, 0.1 mM potassium ferricyanide at pH 5.6, 30 °C CONCLUSION: The bi-enzyme system employed the NADH-ferricyanide dehydrogenase and laccase as catalysts, and potassium ferricyanide as redox mediator, is a promising alternative for NAD(+) regeneration.

The AP2/ERF Transcription Factor DRNL Modulates Gynoecium Development and Affects Its Response to Cytokinin

Directory of Open Access Journals (Sweden)

Yolanda Durán-Medina

2017-10-01

Full Text Available The gynoecium is the female reproductive system in flowering plants. It is a complex structure formed by different tissues, some that are essential for reproduction and others that facilitate the fertilization process and nurture and protect the developing seeds. The coordinated development of these different tissues during the formation of the gynoecium is important for reproductive success. Both hormones and genetic regulators guide the development of the different tissues. Auxin and cytokinin in particular have been found to play important roles in this process. On the other hand, the AP2/ERF2 transcription factor BOL/DRNL/ESR2/SOB is expressed at very early stages of aerial organ formation and has been proposed to be a marker for organ founder cells. In this work, we found that this gene is also expressed at later stages during gynoecium development, particularly at the lateral regions (the region related to the valves of the ovary. The loss of DRNL function affects gynoecium development. Some of the mutant phenotypes present similarities to those observed in plants treated with exogenous cytokinins, and AHP6 has been previously proposed to be a target of DRNL. Therefore, we explored the response of drnl-2 developing gynoecia to cytokinins, and found that the loss of DRNL function affects the response of the gynoecium to exogenously applied cytokinins in a developmental-stage-dependent manner. In summary, this gene participates during gynoecium development, possibly through the dynamic modulation of cytokinin homeostasis and response.

Cytokinins and Expression of SWEET, SUT, CWINV and AAP Genes Increase as Pea Seeds Germinate

Czech Academy of Sciences Publication Activity Database

Jameson, P. E.; Dhandapani, P.; Novák, Ondřej; Song, J.

2016-01-01

Roč. 17, č. 12 (2016), č. článku 2013. E-ISSN 1422-0067 R&D Projects: GA MŠk(CZ) LO1204; GA MŠk LK21306 Institutional support: RVO:61389030 Keywords : cell-wall invertase * sucrose transporter * amino - acids * lupin seeds * corynebacterium-fascians * endogenous cytokinins * stress tolerance * family-members * arabidopsis * metabolism * cytokinin * germination * Pisum sativum Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.226, year: 2016

Shoot- and root-borne cytokinin influences arbuscular mycorrhizal symbiosis

NARCIS (Netherlands)

Rebeca Cosme, M.P.

2016-01-01

The arbuscular mycorrhizal (AM) symbiosis is functionally important for the nutrition and growth of most terrestrial plants. Nearly all phytohormones are employed by plants to regulate the symbiosis with AM fungi, but the regulatory role of cytokinin (CK) is not well understood. Here, we used

Cytokinins and Expression of SWEET, SUT, CWINV and AAP Genes Increase as Pea Seeds Germinate

Directory of Open Access Journals (Sweden)

Paula E. Jameson

2016-12-01

Full Text Available Transporter genes and cytokinins are key targets for crop improvement. These genes are active during the development of the seed and its establishment as a strong sink. However, during germination, the seed transitions to being a source for the developing root and shoot. To determine if the sucrose transporter (SUT, amino acid permease (AAP, Sugar Will Eventually be Exported Transporter (SWEET, cell wall invertase (CWINV, cytokinin biosynthesis (IPT, activation (LOG and degradation (CKX gene family members are involved in both the sink and source activities of seeds, we used RT-qPCR to determine the expression of multiple gene family members, and LC-MS/MS to ascertain endogenous cytokinin levels in germinating Pisum sativum L. We show that genes that are actively expressed when the seed is a strong sink during its development, are also expressed when the seed is in the reverse role of being an active source during germination and early seedling growth. Cytokinins were detected in the imbibing seeds and were actively biosynthesised during germination. We conclude that, when the above gene family members are targeted for seed yield improvement, a downstream effect on subsequent seed germination or seedling vigour must be taken into consideration.

AtSOFL1 and AtSOFL2 act redundantly as positive modulators of the endogenous content of specific cytokinins in Arabidopsis.

Directory of Open Access Journals (Sweden)

Jingyu Zhang

Full Text Available BACKGROUND: Although cytokinins have been known for decades to play important roles in the regulation of plant growth and development, our knowledge of the regulatory mechanism of endogenous content of specific cytokinins remains limited. METHODOLOGY/PRINCIPAL FINDINGS: Here, we characterized two SOB five-like (SOFL genes, AtSOFL1 and AtSOFL2, in Arabidopsis (Arabidopsis thaliana and showed that they acted redundantly in regulating specific cytokinin levels. Analysis of the translational fusion AtSOFL1:AtSOFL1-GUS and AtSOFL2:AtSOFL2-GUS indicated that AtSOFL1 and AtSOFL2 exhibited similar expression patterns. Both proteins were predominantly expressed in the vascular tissues of developing leaves, flowers and siliques, but barely detectable in roots and stems. Overexpression of either AtSOFL1 or AtSOFL2 led to increased cytokinin content and obvious corresponding mutant phenotypes for both transgenic seedlings and adult plants. In addition, overexpression and site-directed mutagenesis experiments demonstrated that the SOFL domains are necessary for AtSOFL2's overexpression phenotypes. Silencing or disrupting either AtSOFL1 or AtSOFL2 caused no obvious developmental defects. Endogenous cytokinin analysis, however, revealed that compared to the wild type control, the SOFL1-RNAi62 sofl2-1 double mutant accumulated lower levels of trans-zeatin riboside monophosphate (tZRMP and N(6-(Delta(2-isopentenyladenosine monophosphate (iPRMP, which are biosynthetic intermediates of bioactive cytokinins. The double mutant also displayed decreased response to exogenous cytokinin in both callus-formation and inhibition-of-hypocotyl-elongation assays. CONCLUSIONS/SIGNIFICANCE: Taken together, our data suggest that in plants AtSOFL1 and AtSOFL2 work redundantly as positive modulators in the fine-tuning of specific cytokinin levels as well as responsiveness.

A somaclonal line SE7 of finger millet (Eleusine coracana) exhibits modified cytokinin homeostasis and increased grain yield

Czech Academy of Sciences Publication Activity Database

Radchuk, V.; Radchuk, R.; Pirko, Y.; Vaňková, Radomíra; Gaudinová, Alena; Korkhovoy, V.; Yemets, A.; Weber, H.; Weschke, W.; Blume, Y. B.

2012-01-01

Roč. 63, č. 15 (2012), s. 5497-5506 ISSN 0022-0957 R&D Projects: GA ČR GA522/09/2058 Institutional research plan: CEZ:AV0Z50380511 Keywords : Cytokinin * cytokinin metabolism * finger millet Subject RIV: ED - Physiology Impact factor: 5.242, year: 2012

Construction of mutant glucose oxidases with increased dye-mediated dehydrogenase activity.

Science.gov (United States)

Horaguchi, Yohei; Saito, Shoko; Kojima, Katsuhiro; Tsugawa, Wakako; Ferri, Stefano; Sode, Koji

2012-11-02

Mutagenesis studies on glucose oxidases (GOxs) were conducted to construct GOxs with reduced oxidase activity and increased dehydrogenase activity. We focused on two representative GOxs, of which crystal structures have already been reported—Penicillium amagasakiense GOx (PDB ID; 1gpe) and Aspergillus niger GOx (PDB ID; 1cf3). We constructed oxygen-interacting structural models for GOxs, and predicted the residues responsible for oxidative half reaction with oxygen on the basis of the crystal structure of cholesterol oxidase as well as on the fact that both enzymes are members of the glucose/methanol/choline (GMC) oxidoreductase family. Rational amino acid substitution resulted in the construction of an engineered GOx with drastically decreased oxidase activity and increased dehydrogenase activity, which was higher than that of the wild-type enzyme. As a result, the dehydrogenase/oxidase ratio of the engineered enzyme was more than 11-fold greater than that of the wild-type enzyme. These results indicate that alteration of the dehydrogenase/oxidase activity ratio of GOxs is possible by introducing a mutation into the putative functional residues responsible for oxidative half reaction with oxygen of these enzymes, resulting in a further increased dehydrogenase activity. This is the first study reporting the alteration of GOx electron acceptor preference from oxygen to an artificial electron acceptor.

Construction of Mutant Glucose Oxidases with Increased Dye-Mediated Dehydrogenase Activity

Science.gov (United States)

Horaguchi, Yohei; Saito, Shoko; Kojima, Katsuhiro; Tsugawa, Wakako; Ferri, Stefano; Sode, Koji

2012-01-01

Mutagenesis studies on glucose oxidases (GOxs) were conducted to construct GOxs with reduced oxidase activity and increased dehydrogenase activity. We focused on two representative GOxs, of which crystal structures have already been reported—Penicillium amagasakiense GOx (PDB ID; 1gpe) and Aspergillus niger GOx (PDB ID; 1cf3). We constructed oxygen-interacting structural models for GOxs, and predicted the residues responsible for oxidative half reaction with oxygen on the basis of the crystal structure of cholesterol oxidase as well as on the fact that both enzymes are members of the glucose/methanol/choline (GMC) oxidoreductase family. Rational amino acid substitution resulted in the construction of an engineered GOx with drastically decreased oxidase activity and increased dehydrogenase activity, which was higher than that of the wild-type enzyme. As a result, the dehydrogenase/oxidase ratio of the engineered enzyme was more than 11-fold greater than that of the wild-type enzyme. These results indicate that alteration of the dehydrogenase/oxidase activity ratio of GOxs is possible by introducing a mutation into the putative functional residues responsible for oxidative half reaction with oxygen of these enzymes, resulting in a further increased dehydrogenase activity. This is the first study reporting the alteration of GOx electron acceptor preference from oxygen to an artificial electron acceptor. PMID:23203056

A potential role of substrate as a base for deprotonation pathway in Rh-catalysed C-H amination of heteroArenes: DFT insights

KAUST Repository

Ajitha, Manjaly John

2016-03-29

The possibility of direct introduction of a new functionality through C–H bond activation is an attractive strategy in covalent synthesis. Here, we investigated the mechanism of Rh-catalysed C-H amination of the hetero-aryl substrate (2-phenylpyridine) using phenyl azide as nitrogen source by density functional theory (DFT). For the deprotocyclometallation and protodecyclometallation processes of the title reaction, we propose a stepwise base-assisted mechanism (pathway I) instead of previously reported concerted mechanism (pathway II). In the new mechanism proposed here, 2-phenylpyridine acts as a base in the initial deprotonation step (C-H bond cleavage) and transports the proton towards the final protonation step. In fact, the N-H bond of the strong conjugate acid (formed during initial C-H bond cleavage) considered in pathway I (via TS4) is more acidic than the C-H bond of the neutral substrate considered in pathway II (via TS5). The higher activation barrier of TS5 mainly originates from the ring strain of the four membered cyclic transition state. The vital role of base, as disclosed here, can potentially have broader mechanistic implications for the development of reaction conditions of transition metal catalysed reactions.

Cytokinin-Deficient Transgenic Arabidopsis Plants Show Multiple Developmental Alterations Indicating Opposite Functions of Cytokinins in the Regulation of Shoot and Root Meristem Activity

Czech Academy of Sciences Publication Activity Database

Werner, T.; Motyka, Václav; Laucou, V.; Smets, R.; Onckelen, H. V.; Schmülling, T.

2003-01-01

Roč. 15, č. 11 (2003), s. 2532-2550 ISSN 1040-4651 R&D Projects: GA AV ČR IAA6038002 Institutional research plan: CEZ:AV0Z5038910 Keywords : Transgenic Arabidopsis Plants * Cytokinins * Root Meristem Activity Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 10.679, year: 2003

Palladium-catalysed electrophilic aromatic C-H fluorination

Science.gov (United States)

Yamamoto, Kumiko; Li, Jiakun; Garber, Jeffrey A. O.; Rolfes, Julian D.; Boursalian, Gregory B.; Borghs, Jannik C.; Genicot, Christophe; Jacq, Jérôme; van Gastel, Maurice; Neese, Frank; Ritter, Tobias

2018-02-01

Aryl fluorides are widely used in the pharmaceutical and agrochemical industries, and recent advances have enabled their synthesis through the conversion of various functional groups. However, there is a lack of general methods for direct aromatic carbon-hydrogen (C-H) fluorination. Conventional methods require the use of either strong fluorinating reagents, which are often unselective and difficult to handle, such as elemental fluorine, or less reactive reagents that attack only the most activated arenes, which reduces the substrate scope. A method for the direct fluorination of aromatic C-H bonds could facilitate access to fluorinated derivatives of functional molecules that would otherwise be difficult to produce. For example, drug candidates with improved properties, such as increased metabolic stability or better blood-brain-barrier penetration, may become available. Here we describe an approach to catalysis and the resulting development of an undirected, palladium-catalysed method for aromatic C-H fluorination using mild electrophilic fluorinating reagents. The reaction involves a mode of catalysis that is unusual in aromatic C-H functionalization because no organometallic intermediate is formed; instead, a reactive transition-metal-fluoride electrophile is generated catalytically for the fluorination of arenes that do not otherwise react with mild fluorinating reagents. The scope and functional-group tolerance of this reaction could provide access to functional fluorinated molecules in pharmaceutical and agrochemical development that would otherwise not be readily accessible.

Analysis of the transcriptional responses in inflorescence buds of Jatropha curcas exposed to cytokinin treatment.

Science.gov (United States)

Chen, Mao-Sheng; Pan, Bang-Zhen; Wang, Gui-Juan; Ni, Jun; Niu, Longjian; Xu, Zeng-Fu

2014-11-30

Jatropha curcas L. is a potential biofuel plant. Application of exogenous cytokinin (6-benzyladenine, BA) on its inflorescence buds can significantly increase the number of female flowers, thereby improving seed yield. To investigate which genes and signal pathways are involved in the response to cytokinin in J. curcas inflorescence buds, we monitored transcriptional activity in inflorescences at 0, 3, 12, 24, and 48 h after BA treatment using a microarray. We detected 5,555 differentially expressed transcripts over the course of the experiment, which could be grouped into 12 distinct temporal expression patterns. We also identified 31 and 131 transcripts in J. curcas whose homologs in model plants function in flowering and phytohormonal signaling pathways, respectively. According to the transcriptional analysis of genes involved in flower development, we hypothesized that BA treatment delays floral organ formation by inhibiting the transcription of the A, B and E classes of floral organ-identity genes, which would allow more time to generate more floral primordia in inflorescence meristems, thereby enhancing inflorescence branching and significantly increasing flower number per inflorescence. BA treatment might also play an important role in maintaining the flowering signals by activating the transcription of GIGANTEA (GI) and inactivating the transcription of CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1) and TERMINAL FLOWER 1b (TFL1b). In addition, exogenous cytokinin treatment could regulate the expression of genes involved in the metabolism and signaling of other phytohormones, indicating that cytokinin and other phytohormones jointly regulate flower development in J. curcas inflorescence buds. Our study provides a framework to better understand the molecular mechanisms underlying changes in flowering traits in response to cytokinin treatment in J. curcas inflorescence buds. The results provide valuable information related to the mechanisms of cross-talk among

Rhodium-catalysed syn-carboamination of alkenes via a transient directing group.

Science.gov (United States)

Piou, Tiffany; Rovis, Tomislav

2015-11-05

Alkenes are the most ubiquitous prochiral functional groups--those that can be converted from achiral to chiral in a single step--that are accessible to synthetic chemists. For this reason, difunctionalization reactions of alkenes (whereby two functional groups are added to the same double bond) are particularly important, as they can be used to produce highly complex molecular architectures. Stereoselective oxidation reactions, including dihydroxylation, aminohydroxylation and halogenation, are well established methods for functionalizing alkenes. However, the intermolecular incorporation of both carbon- and nitrogen-based functionalities stereoselectively across an alkene has not been reported. Here we describe the rhodium-catalysed carboamination of alkenes at the same (syn) face of a double bond, initiated by a carbon-hydrogen activation event that uses enoxyphthalimides as the source of both the carbon and the nitrogen functionalities. The reaction methodology allows for the intermolecular, stereospecific formation of one carbon-carbon and one carbon-nitrogen bond across an alkene, which is, to our knowledge, unprecedented. The reaction design involves the in situ generation of a bidentate directing group and the use of a new cyclopentadienyl ligand to control the reactivity of rhodium. The results provide a new way of synthesizing functionalized alkenes, and should lead to the convergent and stereoselective assembly of amine-containing acyclic molecules.

Cytokinin-induced promotion of root meristem size in the fern Azolla supports a shoot-like origin of euphyllophyte roots.

Science.gov (United States)

de Vries, Jan; Fischer, Angela Melanie; Roettger, Mayo; Rommel, Sophie; Schluepmann, Henriette; Bräutigam, Andrea; Carlsbecker, Annelie; Gould, Sven Bernhard

2016-01-01

The phytohormones cytokinin and auxin orchestrate the root meristem development in angiosperms by determining embryonic bipolarity. Ferns, having the most basal euphyllophyte root, form neither bipolar embryos nor permanent embryonic primary roots but rather an adventitious root system. This raises the questions of how auxin and cytokinin govern fern root system architecture and whether this can tell us something about the origin of that root. Using Azolla filiculoides, we characterized the influence of IAA and zeatin on adventitious fern root meristems and vasculature by Nomarski microscopy. Simultaneously, RNAseq analyses, yielding 36,091 contigs, were used to uncover how the phytohormones affect root tip gene expression. We show that auxin restricts Azolla root meristem development, while cytokinin promotes it; it is the opposite effect of what is observed in Arabidopsis. Global gene expression profiling uncovered 145 genes significantly regulated by cytokinin or auxin, including cell wall modulators, cell division regulators and lateral root formation coordinators. Our data illuminate both evolution and development of fern roots. Promotion of meristem size through cytokinin supports the idea that root meristems of euphyllophytes evolved from shoot meristems. The foundation of these roots was laid in a postembryonically branching shoot system. © 2015 The Authors. New Phytologist © 2015 New Phytologist Trust.

Spatial and temporal changes in endogenous cytokinins in developing pea roots

Czech Academy of Sciences Publication Activity Database

Stirk, W.A.; Novák, Ondřej; Václavíková, Kateřina; Tarkowski, Petr; Strnad, Miroslav; van Staden, J.

2008-01-01

Roč. 227, č. 6 (2008), s. 1279-1289 ISSN 0032-0935 Institutional research plan: CEZ:AV0Z50380511 Keywords : cytokinins * germination * Pisum Subject RIV: CE - Biochemistry Impact factor: 3.088, year: 2008

Stimulatory effect of auxins and cytokinins on carotenes, with differential effects on xanthophylls in the green alga Chlorella pyrenoidosa Chick.

Directory of Open Access Journals (Sweden)

Romuald Czerpak

2014-01-01

Full Text Available Research concerning the influence of auxins and cytokinins on the content of carotenoids in Chlorella pyrenoidosa (Chlorophyceae has been conducted. The strongest stimulating effect on carotenoids content in Ch. pyrenoidosa biomass was exerted by cytokinins (N-6-benzylaminopurine and N-6-furfurylaminopurine and allantoin, weaker by auxins and their chemical analogues, and the weakest by tryptamine and 2,4-dichlorophenoxyacetic acid compared to the control. Under the influence of cytokinins the content of α- and β-carotene have been stimulated several times stronger than by auxins, and especially 2,4- dichlorophenoxyacetic acid and tryptamine. However, oxygen-rich xanthophylls content was most strongly reduced by cytokinins (60-70% in relation to the control in the 20 day lasting of Ch. pyrenoidosa cultivation, similarly to auxins: 1-naphthaleneacetic acid, indole-3-butyric acid, 2,4- dichlorophenoxyacetic acid.

Synthesis of amidoalkyl naphthol via Ritter-type reaction catalysed ...

Indian Academy of Sciences (India)

Multi-component reactions (MCRs) play an important role in organic synthesis since they generally occur in a single pot and exhibit a high atom-economy and selectivity. Ritter-type reaction is an important MCR in organic synthesis for C–N bond forming to afford. N-alkyl amide compounds, which are ubiquitous to a variety ...

Divergent expression of cytokinin biosynthesis, signaling and catabolism genes underlying differences in feeding sites induced by cyst and root-knot nematodes.

Science.gov (United States)

Dowd, Carola D; Chronis, Demosthenis; Radakovic, Zoran S; Siddique, Shahid; Schmülling, Thomas; Werner, Tomáš; Kakimoto, Tatsuo; Grundler, Florian M W; Mitchum, Melissa G

2017-10-01

Cyst and root-knot nematodes are obligate parasites of economic importance with a remarkable ability to reprogram root cells into unique metabolically active feeding sites. Previous studies have suggested a role for cytokinin in feeding site formation induced by these two types of nematodes, but the mechanistic details have not yet been described. Using Arabidopsis as a host plant species, we conducted a comparative analysis of cytokinin genes in response to the beet cyst nematode (BCN), Heterodera schachtii, and the root-knot nematode (RKN), Meloidogyne incognita. We identified distinct differences in the expression of cytokinin biosynthesis, catabolism and signaling genes in response to infection by BCN and RKN, suggesting differential manipulation of the cytokinin pathway by these two nematode species. Furthermore, we evaluated Arabidopsis histidine kinase receptor mutant lines ahk2/3, ahk2/4 and ahk3/4 in response to RKN infection. Similar to our previous studies with BCN, these lines were significantly less susceptible to RKN without compromising nematode penetration, suggesting a requirement of cytokinin signaling in RKN feeding site formation. Moreover, an analysis of ahk double mutants using CycB1;1:GUS/ahk introgressed lines revealed contrasting differences in the cytokinin receptors mediating cell cycle activation in feeding sites induced by BCN and RKN. © 2017 The Authors The Plant Journal © 2017 John Wiley & Sons Ltd.

Cytokinin metabolism in maize: Novel evidence of cytokinin abundance, interconversions and formation of a new trans-zeatin metabolic product with a weak anticytokinin activity

Czech Academy of Sciences Publication Activity Database

Hluska, T.; Dobrev, Petre; Tarkowská, D.; Frébortová, J.; Zalabák, D.; Kopečný, D.; Plíhal, O.; Kokáš, F.; Briozzo, P.; Zatloukal, M.; Motyka, Václav; Galuszka, P.

2016-01-01

Roč. 127, JUN (2016), s. 127-137 ISSN 0168-9452 R&D Projects: GA ČR(CZ) GA16-14649S; GA MŠk(CZ) LO1204 Institutional support: RVO:61389030 Keywords : Anticytokinin * cis-zeatin * Cytokinin Subject RIV: EF - Botanics Impact factor: 3.437, year: 2016

Detection of phytohormones in temperate forest fungi predicts consistent abscisic acid production and a common pathway for cytokinin biosynthesis.

Science.gov (United States)

Morrison, Erin N; Knowles, Sarah; Hayward, Allison; Thorn, R Greg; Saville, Barry J; Emery, R J N

2015-01-01

The phytohormones, abscisic acid and cytokinin, once were thought to be present uniquely in plants, but increasing evidence suggests that these hormones are present in a wide variety of organisms. Few studies have examined fungi for the presence of these "plant" hormones or addressed whether their levels differ based on the nutrition mode of the fungus. This study examined 20 temperate forest fungi of differing nutritional modes (ectomycorrhizal, wood-rotting, saprotrophic). Abscisic acid and cytokinin were present in all fungi sampled; this indicated that the sampled fungi have the capacity to synthesize these two classes of phytohormones. Of the 27 cytokinins analyzed by HPLC-ESI MS/MS, seven were present in all fungi sampled. This suggested the existence of a common cytokinin metabolic pathway in fungi that does not vary among different nutritional modes. Predictions regarding the source of isopentenyl, cis-zeatin and methylthiol CK production stemming from the tRNA degradation pathway among fungi are discussed. © 2015 by The Mycological Society of America.

Cyclin-dependent kinase inhibitor, roscovitine, in combination with exogenous cytokinin, N6-benzyladenine, causes increase of cis-cytokinins in immobilized tobacco cells

Czech Academy of Sciences Publication Activity Database

Blagoeva, Elitsa; Malbeck, Jiří; Gaudinová, Alena; Vaněk, Tomáš; Vaňková, Radomíra

2003-01-01

Roč. 25, č. 6 (2003), s. 469-472 ISSN 0141-5492 R&D Projects: GA MŠk OC 840.20; GA MŠk LN00A081 Institutional research plan: CEZ:AV0Z4055905; CEZ:AV0Z5038910 Keywords : alginate * cytokinins * plant cell immobilization Subject RIV: ED - Physiology Impact factor: 0.778, year: 2003

Anion effect controlling the selectivity in the zinc-catalysed copolymerisation of CO2 and cyclohexene oxide

Directory of Open Access Journals (Sweden)

Sait Elmas

2015-01-01

Full Text Available The choice of the anion has a surprisingly strong effect on the incorporation of CO2 into the polymer obtained during the zinc-catalysed copolymerisation of CO2 and cyclohexene oxide. The product span ranges from polyethercarbonates, where short polyether sequences alternate with carbonate linkages, to polycarbonates with a strictly alternating sequence of the repeating units. Herein, we report on the influence of the coordination ability of the anion on the selectivity and kinetics of the copolymerisation reaction.

Cytokinins in shoot apices of Brassica napus plants during vernalization

Czech Academy of Sciences Publication Activity Database

Tarkowská, Danuše; Filek, M.; Biesaga-Koscielniak, J.; Marcinska, I.; Macháčková, Ivana; Krekule, Jan; Strnad, Miroslav

2012-01-01

Roč. 187, č. 1 (2012), s. 105-112 ISSN 0168-9452 R&D Projects: GA AV ČR KAN200380801; GA MŠk ED0007/01/01 Keywords : Cytokinins * Vernalization * Winter rape * Flowering Subject RIV: EF - Botanics Impact factor: 2.922, year: 2012

Construction of Mutant Glucose Oxidases with Increased Dye-Mediated Dehydrogenase Activity

Directory of Open Access Journals (Sweden)

Koji Sode

2012-11-01

Full Text Available Mutagenesis studies on glucose oxidases (GOxs were conducted to construct GOxs with reduced oxidase activity and increased dehydrogenase activity. We focused on two representative GOxs, of which crystal structures have already been reported—Penicillium amagasakiense GOx (PDB ID; 1gpe and Aspergillus niger GOx (PDB ID; 1cf3. We constructed oxygen-interacting structural models for GOxs, and predicted the residues responsible for oxidative half reaction with oxygen on the basis of the crystal structure of cholesterol oxidase as well as on the fact that both enzymes are members of the glucose/methanol/choline (GMC oxidoreductase family. Rational amino acid substitution resulted in the construction of an engineered GOx with drastically decreased oxidase activity and increased dehydrogenase activity, which was higher than that of the wild-type enzyme. As a result, the dehydrogenase/oxidase ratio of the engineered enzyme was more than 11-fold greater than that of the wild-type enzyme. These results indicate that alteration of the dehydrogenase/oxidase activity ratio of GOxs is possible by introducing a mutation into the putative functional residues responsible for oxidative half reaction with oxygen of these enzymes, resulting in a further increased dehydrogenase activity. This is the first study reporting the alteration of GOx electron acceptor preference from oxygen to an artificial electron acceptor.

Effect of abiotic stresses on the activity of antioxidative enzymes and contents of phytohormones in wild type and AtCKX2 transgenic tobacco plants

Czech Academy of Sciences Publication Activity Database

Mýtinová, Zuzana; Motyka, Václav; Haisel, Daniel; Gaudinová, Alena; Lubovská, Zuzana; Wilhelmová, Naděžda

2010-01-01

Roč. 54, č. 3 (2010), s. 461-470 ISSN 0006-3134 R&D Projects: GA ČR GA522/03/0312; GA ČR GA206/06/1306 Institutional research plan: CEZ:AV0Z50380511 Keywords : abscisic acid * cytokinin * cytokinin oxidase/dehydrogenase Subject RIV: CE - Biochemistry Impact factor: 1.582, year: 2010

Light influences cytokinin biosynthesis and sensing in Nostoc (cyanobacteria)

Czech Academy of Sciences Publication Activity Database

Frébortová, J.; Plíhal, O.; Florová, P.; Kokáš, F.; Kubiasová, K.; Greplová, M.; Šimura, J.; Novák, Ondřej; Frébort, I.

2017-01-01

Roč. 53, č. 3 (2017), s. 703-714 ISSN 0022-3646 R&D Projects: GA MŠk(CZ) LO1204 Institutional support: RVO:61389030 Keywords : cytokinin * expression profiling * miaA * Nostoc * RNA-seq * sensor kinase * tRNA IPT Subject RIV: EB - Genetics ; Molecular Biology OBOR OECD: Plant sciences, botany Impact factor: 2.608, year: 2016

DFT-based prediction of reactivity of short-chain alcohol dehydrogenase

Science.gov (United States)

Stawoska, I.; Dudzik, A.; Wasylewski, M.; Jemioła-Rzemińska, M.; Skoczowski, A.; Strzałka, K.; Szaleniec, M.

2017-06-01

The reaction mechanism of ketone reduction by short chain dehydrogenase/reductase, ( S)-1-phenylethanol dehydrogenase from Aromatoleum aromaticum, was studied with DFT methods using cluster model approach. The characteristics of the hydride transfer process were investigated based on reaction of acetophenone and its eight structural analogues. The results confirmed previously suggested concomitant transfer of hydride from NADH to carbonyl C atom of the substrate with proton transfer from Tyr to carbonyl O atom. However, additional coupled motion of the next proton in the proton-relay system, between O2' ribose hydroxyl and Tyr154 was observed. The protonation of Lys158 seems not to affect the pKa of Tyr154, as the stable tyrosyl anion was observed only for a neutral Lys158 in the high pH model. The calculated reaction energies and reaction barriers were calibrated by calorimetric and kinetic methods. This allowed an excellent prediction of the reaction enthalpies (R2 = 0.93) and a good prediction of the reaction kinetics (R2 = 0.89). The observed relations were validated in prediction of log K eq obtained for real whole-cell reactor systems that modelled industrial synthesis of S-alcohols.

Biochemical characterization of a recombinant short-chain NAD(H)-dependent dehydrogenase/reductase from Sulfolobus acidocaldarius.

Science.gov (United States)

Pennacchio, Angela; Giordano, Assunta; Pucci, Biagio; Rossi, Mosè; Raia, Carlo A

2010-03-01

The gene encoding a novel alcohol dehydrogenase that belongs to the short-chain dehydrogenases/reductases (SDRs) superfamily was identified in the aerobic thermoacidophilic crenarchaeon Sulfolobus acidocaldarius strain DSM 639. The saadh gene was heterologously overexpressed in Escherichia coli, and the protein (SaADH) was purified to homogeneity and characterized. SaADH is a tetrameric enzyme consisting of identical 28,978-Da subunits, each composed of 264 amino acids. The enzyme has remarkable thermophilicity and thermal stability, displaying activity at temperatures up to 75 degrees C and a 30-min half-inactivation temperature of ~90 degrees C, and shows good tolerance to common organic solvents. SaADH has a strict requirement for NAD(H) as the coenzyme, and displays a preference for the reduction of alicyclic, bicyclic and aromatic ketones and alpha-keto esters, but is poorly active on aliphatic, cyclic and aromatic alcohols, and shows no activity on aldehydes. The enzyme catalyses the reduction of alpha-methyl and alpha-ethyl benzoylformate, and methyl o-chlorobenzoylformate with 100% conversion to methyl (S)-mandelate [17% enantiomeric excess (ee)], ethyl (R)-mandelate (50% ee), and methyl (R)-o-chloromandelate (72% ee), respectively, with an efficient in situ NADH-recycling system which involves glucose and a thermophilic glucose dehydrogenase. This study provides further evidence supporting the critical role of the D37 residue in discriminating NAD(H) from NAD(P)H in members of the SDR superfamily.

Direct Electron Transfer of Dehydrogenases for Development of 3rd Generation Biosensors and Enzymatic Fuel Cells

Directory of Open Access Journals (Sweden)

Paolo Bollella

2018-04-01

Full Text Available Dehydrogenase based bioelectrocatalysis has been increasingly exploited in recent years in order to develop new bioelectrochemical devices, such as biosensors and biofuel cells, with improved performances. In some cases, dehydrogeases are able to directly exchange electrons with an appropriately designed electrode surface, without the need for an added redox mediator, allowing bioelectrocatalysis based on a direct electron transfer process. In this review we briefly describe the electron transfer mechanism of dehydrogenase enzymes and some of the characteristics required for bioelectrocatalysis reactions via a direct electron transfer mechanism. Special attention is given to cellobiose dehydrogenase and fructose dehydrogenase, which showed efficient direct electron transfer reactions. An overview of the most recent biosensors and biofuel cells based on the two dehydrogenases will be presented. The various strategies to prepare modified electrodes in order to improve the electron transfer properties of the device will be carefully investigated and all analytical parameters will be presented, discussed and compared.

Gold(I)-Catalysed Hydroarylation of 1,3-Disubstituted Allenes with Efficient Axial-to-Point Chirality Transfer.

Science.gov (United States)

Sutherland, Daniel R; Kinsman, Luke; Angiolini, Stuart M; Rosair, Georgina M; Lee, Ai-Lan

2018-05-11

Hydroarylation of enantioenriched 1,3-disubstituted allenes has the potential to proceed with axial-to-point chirality transfer to yield enantioenriched allylated (hetero)aryl compounds. However, the gold-catalysed intermolecular reaction was previously reported to occur with no chirality transfer owing to competing allene racemisation. Herein, we describe the development of the first intermolecular hydroarylations of allenes to proceed with efficient chirality transfer and summarise some of the key criteria for achieving high regio- and stereoselectivity. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

High cytokinin levels induce a hypersensitive-like response in tobacco

Czech Academy of Sciences Publication Activity Database

Novák, J.; Pavlů, J.; Novák, Ondřej; Nožková-Hlaváčková, V.; Špundová, M.; Hlavinka, J.; Koukalová, Š.; Skalák, J.; Černý, M.; Brzobohatý, B.

2013-01-01

Roč. 112, č. 1 (2013), s. 41-55 ISSN 0305-7364 R&D Projects: GA MŠk 1M06030; GA MŠk LK21306 Institutional support: RVO:61389030 Keywords : Cytokinin * hypersensitive response * hydrogen peroxide Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.295, year: 2013

Changes in transcription of cytokinin metabolism and signalling genes in grape (Vitis vinifera L.) berries are associated with the ripening-related increase in isopentenyladenine.

Science.gov (United States)

Böttcher, Christine; Burbidge, Crista A; Boss, Paul K; Davies, Christopher

2015-09-16

Cytokinins are known to play an important role in fruit set and early fruit growth, but their involvement in later stages of fruit development is less well understood. Recent reports of greatly increased cytokinin concentrations in the flesh of ripening kiwifruit (Actinidia deliciosa (A. Chev.) C.F. Liang & A.R. Ferguson) and grapes (Vitis vinifera L.) have suggested that these hormones are implicated in the control of ripening-related processes. A similar pattern of isopentenyladenine (iP) accumulation was observed in the ripening fruit of several grapevine cultivars, strawberry (Fragaria ananassa Duch.) and tomato (Solanum lycopersicum Mill.), suggesting a common, ripening-related role for this cytokinin. Significant differences in maximal iP concentrations between grapevine cultivars and between fruit species might reflect varying degrees of relevance or functional adaptations of this hormone in the ripening process. Grapevine orthologues of five Arabidopsis (Arabidopsis thaliana L.) gene families involved in cytokinin metabolism and signalling were identified and analysed for their expression in developing grape berries and a range of other grapevine tissues. Members of each gene family were characterised by distinct expression profiles during berry development and in different grapevine organs, suggesting a complex regulation of cellular cytokinin activities throughout the plant. The post-veraison-specific expression of a set of biosynthesis, activation, perception and signalling genes together with a lack of expression of degradation-related genes during the ripening phase were indicative of a local control of berry iP concentrations leading to the observed accumulation of iP in ripening grapes. The transcriptional analysis of grapevine genes involved in cytokinin production, degradation and response has provided a possible explanation for the ripening-associated accumulation of iP in grapes and other fruit. The pre- and post-veraison-specific expression of

Vanillin formation from ferulic acid in Vanilla planifolia is catalysed by a single enzyme

Science.gov (United States)

Gallage, Nethaji J.; Hansen, Esben H.; Kannangara, Rubini; Olsen, Carl Erik; Motawia, Mohammed Saddik; Jørgensen, Kirsten; Holme, Inger; Hebelstrup, Kim; Grisoni, Michel; Møller, Birger Lindberg

2014-01-01

Vanillin is a popular and valuable flavour compound. It is the key constituent of the natural vanilla flavour obtained from cured vanilla pods. Here we show that a single hydratase/lyase type enzyme designated vanillin synthase (VpVAN) catalyses direct conversion of ferulic acid and its glucoside into vanillin and its glucoside, respectively. The enzyme shows high sequence similarity to cysteine proteinases and is specific to the substitution pattern at the aromatic ring and does not metabolize caffeic acid and p-coumaric acid as demonstrated by coupled transcription/translation assays. VpVAN localizes to the inner part of the vanilla pod and high transcript levels are found in single cells located a few cell layers from the inner epidermis. Transient expression of VpVAN in tobacco and stable expression in barley in combination with the action of endogenous alcohol dehydrogenases and UDP-glucosyltransferases result in vanillyl alcohol glucoside formation from endogenous ferulic acid. A gene encoding an enzyme showing 71% sequence identity to VpVAN was identified in another vanillin-producing plant species Glechoma hederacea and was also shown to be a vanillin synthase as demonstrated by transient expression in tobacco. PMID:24941968

General-base catalysed hydrolysis and nucleophilic substitution of activated amides in aqueous solutions

NARCIS (Netherlands)

Buurma, NJ; Blandamer, MJ; Engberts, JBFN; Buurma, Niklaas J.

The reactivity of 1-benzoyl-3-phenyl-1,2,4-triazole (1a) was studied in the presence of a range of weak bases in aqueous solution. A change in mechanism is observed from general-base catalysed hydrolysis to nucleophilic substitution and general-base catalysed nucleophilic substitution. A slight

The recovery of cytokinins during extraction and purification of clubroot tissue

NARCIS (Netherlands)

Dekhuijzen, H.M.; Gevers, E.C.T.

1975-01-01

Losses of one naturally occurring cytokinin (zeatin) and one synthetic cytoknin (kinetin) were determined during purification of turnips (Brassica compestris) infected by Plasmodiophora brassicae (clubroot). A known amount of zeatin and 8‐14C‐kinetin was added after homogenization of plant material

Influence of root-bed size on the response of tobacco to elevated CO2 as mediated by cytokinins

Science.gov (United States)

Schaz, Ulrike; Düll, Barbara; Reinbothe, Christiane; Beck, Erwin

2014-01-01

The extent of growth stimulation of C3 plants by elevated CO2 is modulated by environmental factors. Under optimized environmental conditions (high light, continuous water and nutrient supply, and others), we analysed the effect of an elevated CO2 atmosphere (700 ppm, EC) and the importance of root-bed size on the growth of tobacco. Biomass production was consistently higher under EC. However, the stimulation was overridden by root-bed volumes that restricted root growth. Maximum growth and biomass production were obtained at a root bed of 15 L at ambient and elevated CO2 concentrations. Starting with seed germination, the plants were strictly maintained under ambient or elevated CO2 until flowering. Thus, the well-known acclimation effect of growth to enhanced CO2 did not occur. The relative growth rates of EC plants exceeded those of ambient-CO2 plants only during the initial phases of germination and seedling establishment. This was sufficient for a persistently higher absolute biomass production by EC plants in non-limiting root-bed volumes. Both the size of the root bed and the CO2 concentration influenced the quantitative cytokinin patterns, particularly in the meristematic tissues of shoots, but to a smaller extent in stems, leaves and roots. In spite of the generally low cytokinin concentrations in roots, the amounts of cytokinins moving from the root to the shoot were substantially higher in high-CO2 plants. Because the cytokinin patterns of the (xylem) fluid in the stems did not match those of the shoot meristems, it is assumed that cytokinins as long-distance signals from the roots stimulate meristematic activity in the shoot apex and the sink leaves. Subsequently, the meristems are able to synthesize those phytohormones that are required for the cell cycle. Root-borne cytokinins entering the shoot appear to be one of the major control points for the integration of various environmental cues into one signal for optimized growth. PMID:24790131

Mediatorless electron transfer in glucose dehydrogenase/laccase system adsorbed on carbon nanotubes

International Nuclear Information System (INIS)

Ratautas, D.; Marcinkevičienė, L.; Meškys, R.; Kulys, J.

2015-01-01

Highlights: • Glucose dehydrogenase from Ewingella americana (GDH) demonstrated an effective mediatorless oxidation of glucose on single-walled carbon nanotubes (SWCNT). • Laccase from Trichaptum abietinum (LAC) exhibited mediatorless oxygen reduction when the enzyme was adsorbed on SWCNT. • Simultaneous adsorption of GDH and LAC on SWCNT formed an electron transfer chain in which glucose and lactose were oxidized by oxygen in mediatorless manner. - Abstract: A mediatorless electron transfer in the chain of glucose dehydrogenase (GDH) and laccase (LAC) catalysing the oxidation of glucose by molecular oxygen was studied. To demonstrate mediatorless processes, the GDH from Ewingella americana was adsorbed on single-walled carbon nanotubes (SWCNT). The effective mediatorless oxidation of glucose proceeded at 0.2–0.4 V vs. SCE. The electrode was most active at pH 6.1, and generated 0.8 mA cm −2 biocatalytic current in the presence of 50 mM glucose. The electrode showed a bell-shaped pH dependence with pK a values of 4.1 and 7.5. LAC from Trichaptum abietinum adsorbed on SWCNT exhibited mediatorless oxygen reduction at electrode potential less than 0.65 V. The electrode was most active at pH 3.0–4.0 and generated 1.1 mA cm −2 biocatalytic current in the presence of 0.254 mM oxygen, with an apparent pK a of 1.0 and 5.4. The electrodes prepared by simultaneous adsorption of GDH and LAC on SWCNT exhibited glucose oxidation at a potential higher than 0.25 V. The oxygen consumption in the chain was demonstrated using a Clark-type oxygen electrode. The dependence of oxygen consumption on glucose and lactose concentrations as well as activity of the system on pH were measured. A model of the pH dependence as well as mediatorless consecutive glucose oxidation with oxygen catalysed by LAC/GDH system is presented. This work provides a novel approach towards the synthesis of artificial multi enzyme systems by wiring oxidoreductases with SWCNT, and offers a better

INTERACTION OF AROMATIC CYTOKININS WITH HUMAN LIVER MICROSOMAL CYTOCHROMES P450

Czech Academy of Sciences Publication Activity Database

Anzenbacherová, E.; Janalík, J.; Popa, Igor; Strnad, Miroslav; Anzenbacher, P.

2005-01-01

Roč. 149, č. 2 (2005), s. 349-351 ISSN 1213-8118 Institutional research plan: CEZ:AV0Z50380511 Keywords : Cytokinins * Cyclin dependent kinase inhibitor * Cytochrome P450 Subject RIV: CE - Biochemistry http://publib.upol.cz/~obd/fulltext/Biomed/2005/2/349.pdf

Kinetic and thermodynamic study of the reaction catalyzed by glucose-6-phosphate dehydrogenase with nicotinamide adenine dinucleotide

International Nuclear Information System (INIS)

Martin del Campo, Julia S.; Patino, Rodrigo

2011-01-01

Research highlights: → The reaction catalyzed by one enzyme of the pentose phosphate pathway was studied. → A spectrophotometric method is proposed for kinetic and thermodynamic analysis. → The pH and the temperature influences are reported on physical chemical properties. → Relative concentrations of substrates are also important in the catalytic process. - Abstract: The enzyme glucose-6-phosphate dehydrogenase (G6PD, EC 1.1.1.49) from Leuconostoc mesenteroides has a dual coenzyme specificity with oxidized nicotinamide adenine dinucleotide (NAD ox ) and oxidized nicotinamide adenine dinucleotide phosphate as electron acceptors. The G6PD coenzyme selection is determined by the metabolic cellular prevailing conditions. In this study a kinetic and thermodynamic analysis is presented for the reaction catalyzed by G6PD from L. mesenteroides with NAD ox as coenzyme in phosphate buffer. For this work, an in situ spectrophotometric technique was employed based on the detection of one product of the reaction. Substrate and coenzyme concentrations as well as temperature and pH effects were evaluated. The apparent equilibrium constant, the Michaelis constant, and the turnover number were determined as a function of each experimental condition. The standard transformed Gibbs energy of reaction was determined from equilibrium constants at different initial conditions. For the product 6-phospho-D-glucono-1,5-lactone, a value of the standard Gibbs energy of formation is proposed, Δ f G o = -1784 ± 5 kJ mol -1 .

Co-solvent effects on reaction rate and reaction equilibrium of an enzymatic peptide hydrolysis.

Science.gov (United States)

Wangler, A; Canales, R; Held, C; Luong, T Q; Winter, R; Zaitsau, D H; Verevkin, S P; Sadowski, G

2018-04-25

This work presents an approach that expresses the Michaelis constant KaM and the equilibrium constant Kth of an enzymatic peptide hydrolysis based on thermodynamic activities instead of concentrations. This provides KaM and Kth values that are independent of any co-solvent. To this end, the hydrolysis reaction of N-succinyl-l-phenylalanine-p-nitroanilide catalysed by the enzyme α-chymotrypsin was studied in pure buffer and in the presence of the co-solvents dimethyl sulfoxide, trimethylamine-N-oxide, urea, and two salts. A strong influence of the co-solvents on the measured Michaelis constant (KM) and equilibrium constant (Kx) was observed, which was found to be caused by molecular interactions expressed as activity coefficients. Substrate and product activity coefficients were used to calculate the activity-based values KaM and Kth for the co-solvent free reaction. Based on these constants, the co-solvent effect on KM and Kx was predicted in almost quantitative agreement with the experimental data. The approach presented here does not only reveal the importance of understanding the thermodynamic non-ideality of reactions taking place in biological solutions and in many technological applications, it also provides a framework for interpreting and quantifying the multifaceted co-solvent effects on enzyme-catalysed reactions that are known and have been observed experimentally for a long time.

Kinetic and thermodynamic study of the reaction catalyzed by glucose-6-phosphate dehydrogenase with nicotinamide adenine dinucleotide

Energy Technology Data Exchange (ETDEWEB)

Martin del Campo, Julia S. [Departamento de Fisica Aplicada, Centro de Investigacion y de Estudios Avanzados - Unidad Merida, Carretera antigua a Progreso Km. 6, A.P. 73 Cordemex, 97310, Merida, Yucatan (Mexico); Patino, Rodrigo, E-mail: rtarkus@mda.cinvestav.mx [Departamento de Fisica Aplicada, Centro de Investigacion y de Estudios Avanzados - Unidad Merida, Carretera antigua a Progreso Km. 6, A.P. 73 Cordemex, 97310, Merida, Yucatan (Mexico)

2011-04-20

Research highlights: {yields} The reaction catalyzed by one enzyme of the pentose phosphate pathway was studied. {yields} A spectrophotometric method is proposed for kinetic and thermodynamic analysis. {yields} The pH and the temperature influences are reported on physical chemical properties. {yields} Relative concentrations of substrates are also important in the catalytic process. - Abstract: The enzyme glucose-6-phosphate dehydrogenase (G6PD, EC 1.1.1.49) from Leuconostoc mesenteroides has a dual coenzyme specificity with oxidized nicotinamide adenine dinucleotide (NAD{sub ox}) and oxidized nicotinamide adenine dinucleotide phosphate as electron acceptors. The G6PD coenzyme selection is determined by the metabolic cellular prevailing conditions. In this study a kinetic and thermodynamic analysis is presented for the reaction catalyzed by G6PD from L. mesenteroides with NAD{sub ox} as coenzyme in phosphate buffer. For this work, an in situ spectrophotometric technique was employed based on the detection of one product of the reaction. Substrate and coenzyme concentrations as well as temperature and pH effects were evaluated. The apparent equilibrium constant, the Michaelis constant, and the turnover number were determined as a function of each experimental condition. The standard transformed Gibbs energy of reaction was determined from equilibrium constants at different initial conditions. For the product 6-phospho-D-glucono-1,5-lactone, a value of the standard Gibbs energy of formation is proposed, {Delta}{sub f}G{sup o} = -1784 {+-} 5 kJ mol{sup -1}.

Seedlings of medicinal plants treated with either a cytokinin antagonist (PI-55) or an inhibitor of cytokinin degradation (INCYDE) are protected against the negative effects of cadmium

Czech Academy of Sciences Publication Activity Database

Gemrotová, Markéta; Kulkarni, M. G.; Stirk, W. A.; Strnad, Miroslav; van Staden, J.; Spíchal, Lukáš

2013-01-01

Roč. 71, č. 2 (2013), s. 137-145 ISSN 0167-6903 R&D Projects: GA MŠk(CZ) LC06034 Institutional research plan: CEZ:AV0Z50380511 Keywords : Cytokinin * Heavy metals * Cadmium Subject RIV: ED - Physiology Impact factor: 1.625, year: 2013

On the Mechanism of the Digold(I)-Hydroxide-Catalysed Hydrophenoxylation of Alkynes

KAUST Repository

Gómez-Suárez, Adrián

2015-12-13

Herein, we present a detailed investigation of the mechanistic aspects of the dual gold-catalysed hydrophenoxylation of alkynes by both experimental and computational methods. The dissociation of [{Au(NHC)}2(μ-OH)][BF4] is essential to enter the catalytic cycle, and this step is favoured by the presence of bulky, non-coordinating counter ions. Moreover, in silico studies confirmed that phenol does not only act as a reactant, but also as a co-catalyst, lowering the energy barriers of several transition states. A gem-diaurated species might form during the reaction, but this lies deep within a potential energy well, and is likely to be an "off-cycle" rather than an "in-cycle" intermediate. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

On the Mechanism of the Digold(I)-Hydroxide-Catalysed Hydrophenoxylation of Alkynes.

Science.gov (United States)

Gómez-Suárez, Adrián; Oonishi, Yoshihiro; Martin, Anthony R; Vummaleti, Sai V C; Nelson, David J; Cordes, David B; Slawin, Alexandra M Z; Cavallo, Luigi; Nolan, Steven P; Poater, Albert

2016-01-18

Herein, we present a detailed investigation of the mechanistic aspects of the dual gold-catalysed hydrophenoxylation of alkynes by both experimental and computational methods. The dissociation of [{Au(NHC)}2 (μ-OH)][BF4 ] is essential to enter the catalytic cycle, and this step is favoured by the presence of bulky, non-coordinating counter ions. Moreover, in silico studies confirmed that phenol does not only act as a reactant, but also as a co-catalyst, lowering the energy barriers of several transition states. A gem-diaurated species might form during the reaction, but this lies deep within a potential energy well, and is likely to be an "off-cycle" rather than an "in-cycle" intermediate. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Flavonoids and Auxin Transport Inhibitors Rescue Symbiotic Nodulation in the Medicago truncatula Cytokinin Perception Mutant cre1

Science.gov (United States)

Ng, Jason Liang Pin; Hassan, Samira; Truong, Thy T.; Hocart, Charles H.; Laffont, Carole; Frugier, Florian; Mathesius, Ulrike

2015-01-01

Initiation of symbiotic nodules in legumes requires cytokinin signaling, but its mechanism of action is largely unknown. Here, we tested whether the failure to initiate nodules in the Medicago truncatula cytokinin perception mutant cre1 (cytokinin response1) is due to its altered ability to regulate auxin transport, auxin accumulation, and induction of flavonoids. We found that in the cre1 mutant, symbiotic rhizobia cannot locally alter acro- and basipetal auxin transport during nodule initiation and that these mutants show reduced auxin (indole-3-acetic acid) accumulation and auxin responses compared with the wild type. Quantification of flavonoids, which can act as endogenous auxin transport inhibitors, showed a deficiency in the induction of free naringenin, isoliquiritigenin, quercetin, and hesperetin in cre1 roots compared with wild-type roots 24 h after inoculation with rhizobia. Coinoculation of roots with rhizobia and the flavonoids naringenin, isoliquiritigenin, and kaempferol, or with the synthetic auxin transport inhibitor 2,3,5,-triiodobenzoic acid, rescued nodulation efficiency in cre1 mutants and allowed auxin transport control in response to rhizobia. Our results suggest that CRE1-dependent cytokinin signaling leads to nodule initiation through the regulation of flavonoid accumulation required for local alteration of polar auxin transport and subsequent auxin accumulation in cortical cells during the early stages of nodulation. PMID:26253705

Function of plant defense secondary metabolite in cytokinin degradation

Czech Academy of Sciences Publication Activity Database

Frébortová, Jitka

2010-01-01

Roč. 5, č. 5 (2010), s. 523-525 ISSN 1559-2316 R&D Projects: GA ČR GA522/05/0448; GA ČR GA301/08/1649 Institutional research plan: CEZ:AV0Z50380511 Keywords : cytokinin dehydrogenace * 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one * phenoxyl radiál Subject RIV: EF - Botanics http://www.landesbioscience.com/journals/psb/article/10965/

Unprecedented Carbonato Intermediates in Cyclic Carbonate Synthesis Catalysed by Bimetallic Aluminium(Salen) Complexes.

Science.gov (United States)

Castro-Osma, José A; North, Michael; Offermans, Willem K; Leitner, Walter; Müller, Thomas E

2016-04-21

The mechanism by which [Al(salen)]2 O complexes catalyse the synthesis of cyclic carbonates from epoxides and carbon dioxide in the absence of a halide cocatalyst has been investigated. Density functional theory (DFT) studies, mass spectrometry and (1) H NMR, (13) C NMR and infrared spectroscopies provide evidence for the formation of an unprecedented carbonato bridged bimetallic aluminium complex which is shown to be a key intermediate for the halide-free synthesis of cyclic carbonates from epoxides and carbon dioxide. Deuterated and enantiomerically-pure epoxides were used to study the reaction pathway. Based on the experimental and theoretical results, a catalytic cycle is proposed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The radiation inactivation of glutamate and isocitrate dehydrogenases

International Nuclear Information System (INIS)

El Failat, R.R.A.

1980-12-01

The reaction of free radicals produced by ionizing radiation with the enzymes glutamate dehydrogenase (GDH) and NADP + -specific isocitrate dehydrogenase (ICDH) have been studied by steady-state and pulse radiolysis techniques. In de-aerated GDH solutions, hydroxyl radicals have been found to be the most efficient of the primary radicals generated from water in causing inactivation. The effect of reaction with the enzyme of selective free radicals (SCN) 2 - , (Br) 2 - and (I) 2 - on its activity has also been studied. In neutral solutions, the order of inactivating effectiveness is (I) 2 - > (Br) 2 - > (SCN) 2 - . In the case of the thiocyanate radical anion (SCN) 2 - , the inactivation efficiency is found to depend on KSCN concentration. The radiation inactivation of GDH at both neutral and alkaline pH is accompanied by the loss of sulphydryl groups. Pulse radiolysis was also used to determine the rate constants and the transient absorption spectra following the reaction of the free radicals with GDH. 60 Co-γ-radiolysis and pulse radiolysis were also used to study the effect of ionizing radiation on the activity of ICDH. The results obtained were similar to those of GDH. (author)

ald of Mycobacterium tuberculosis Encodes both the Alanine Dehydrogenase and the Putative Glycine Dehydrogenase

Science.gov (United States)

Giffin, Michelle M.; Modesti, Lucia; Raab, Ronald W.; Wayne, Lawrence G.

2012-01-01

The putative glycine dehydrogenase of Mycobacterium tuberculosis catalyzes the reductive amination of glyoxylate to glycine but not the reverse reaction. The enzyme was purified and identified as the previously characterized alanine dehydrogenase. The Ald enzyme was expressed in Escherichia coli and had both pyruvate and glyoxylate aminating activities. The gene, ald, was inactivated in M. tuberculosis, which resulted in the loss of all activities. Both enzyme activities were found associated with the cell and were not detected in the extracellular filtrate. By using an anti-Ald antibody, the protein was localized to the cell membrane, with a smaller fraction in the cytosol. None was detected in the extracellular medium. The ald knockout strain grew without alanine or glycine and was able to utilize glycine but not alanine as a nitrogen source. Transcription of ald was induced when alanine was the sole nitrogen source, and higher levels of Ald enzyme were measured. Ald is proposed to have several functions, including ammonium incorporation and alanine breakdown. PMID:22210765

Different specificities of two aldehyde dehydrogenases from Saccharomyces cerevisiae var. boulardii.

Science.gov (United States)

Datta, Suprama; Annapure, Uday S; Timson, David J

2017-04-30

Aldehyde dehydrogenases play crucial roles in the detoxification of exogenous and endogenous aldehydes by catalysing their oxidation to carboxylic acid counterparts. The present study reports characterization of two such isoenzymes from the yeast Saccharomyces cerevisiae var. boulardii (NCYC 3264), one mitochondrial (Ald4p) and one cytosolic (Ald6p). Both Ald4p and Ald6p were oligomeric in solution and demonstrated positive kinetic cooperativity towards aldehyde substrates. Wild-type Ald6p showed activity only with aliphatic aldehydes. Ald4p, on the contrary, showed activity with benzaldehyde along with a limited range of aliphatic aldehydes. Inspection of modelled structure of Ald6p revealed that a bulky amino acid residue (Met 177 , compared with the equivalent residue Leu 196 in Ald4p) might cause steric hindrance of cyclic substrates. Therefore, we hypothesized that specificities of the two isoenzymes towards aldehyde substrates were partly driven by steric hindrance in the active site. A variant of wild-type Ald6p with the Met 177 residue replaced by a valine was also characterized to address to the hypothesis. It showed an increased specificity range and a gain of activity towards cyclohexanecarboxaldehyde. It also demonstrated an increased thermal stability when compared with both the wild-types. These data suggest that steric bulk in the active site of yeast aldehyde dehydrogenases is partially responsible for controlling specificity. © 2017 The Author(s).

pH-dependent electron transfer reaction and direct bioelectrocatalysis of the quinohemoprotein pyranose dehydrogenase

Energy Technology Data Exchange (ETDEWEB)

Takeda, Kouta [Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588 (Japan); Matsumura, Hirotoshi; Ishida, Takuya [Department of Biomaterial Sciences, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657 (Japan); Yoshida, Makoto [Department of Environmental and Natural Resource Science, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509 (Japan); Igarashi, Kiyohiko; Samejima, Masahiro [Department of Biomaterial Sciences, Graduate School of Agriculture and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo 113-8657 (Japan); Ohno, Hiroyuki [Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588 (Japan); Nakamura, Nobuhumi, E-mail: nobu1@cc.tuat.ac.jp [Department of Biotechnology and Life Science, Tokyo University of Agriculture and Technology, Koganei, Tokyo 184-8588 (Japan)

2016-08-26

A pyranose dehydrogenase from Coprinopsis cinerea (CcPDH) is an extracellular quinohemoeprotein, which consists a b-type cytochrome domain, a pyrroloquinoline-quinone (PQQ) domain, and a family 1-type carbohydrate-binding module. The electron transfer reaction of CcPDH was studied using some electron acceptors and a carbon electrode at various pH levels. Phenazine methosulfate (PMS) reacted directly at the PQQ domain, whereas cytochrome c (cyt c) reacted via the cytochrome domain of intact CcPDH. Thus, electrons are transferred from reduced PQQ in the catalytic domain of CcPDH to heme b in the N-terminal cytochrome domain, which acts as a built-in mediator and transfers electron to a heterogenous electron transfer protein. The optimal pH values of the PMS reduction (pH 6.5) and the cyt c reduction (pH 8.5) differ. The catalytic currents for the oxidation of L-fucose were observed within a range of pH 4.5 to 11. Bioelectrocatalysis of CcPDH based on direct electron transfer demonstrated that the pH profile of the biocatalytic current was similar to the reduction activity of cyt c characters. - Highlights: • pH dependencies of activity were different for the reduction of cyt c and DCPIP. • DET-based bioelectrocatalysis of CcPDH was observed. • The similar pH-dependent profile was found with cyt c and electrode. • The present results suggested that IET reaction of CcPDH shows pH dependence.

Endogenous cytokinins, auxins, and abscisic acid in red algae from Brazil

Czech Academy of Sciences Publication Activity Database

Yokoya, N. S.; Stirk, W. A.; van Staden, J.; Novák, Ondřej; Turečková, Veronika; Pěnčík, Aleš; Strnad, Miroslav

2010-01-01

Roč. 46, č. 6 (2010), s. 1198-1205 ISSN 0022-3646 R&D Projects: GA ČR GA301/08/1649 Institutional research plan: CEZ:AV0Z50380511 Keywords : ENDOGENOUS * CYTOKININS * AUXINS * ABSCISIC ACID * RED * ALGAE * BRAZIL Subject RIV: EF - Botanics Impact factor: 2.239, year: 2010

Chiral amides via copper-catalysed enantioselective conjugate addition

NARCIS (Netherlands)

Schoonen, Anne K.; Fernández-Ibáñez, M. Ángeles; Fañanás-Mastral, Martín; Teichert, Johannes F.; Feringa, Bernard

2014-01-01

A highly enantioselective one pot procedure for the synthesis of beta-substituted amides was developed starting from the corresponding alpha,beta-unsaturated esters. This new methodology is based on the copper-catalysed enantioselective conjugate addition of Grignard reagents to

Homology modelling and docking analysis of L-lactate dehydrogenase from Streptococcus thermopilus

Directory of Open Access Journals (Sweden)

Vukić Vladimir R.

2016-01-01

Full Text Available The aim of this research was to create a three-dimensional model of L-lactate dehydrogenase from the main yoghurt starter culture - Streptococcus thermopilus, to analyse its structural features and investigate substrate binding in the active site. NCBI BlastP was used against the Protein Data Bank database in order to identify the template for construction of homology models. Multiple sequence alignment was performed using the program MUSCULE within the UGENE 1.11.3 program. Homology models were constructed using the program Modeller v. 9.17. The obtained 3D model was verified by Ramachandran plots. Molecular docking simulations were performed using the program Surflex-Dock. The highest sequence similarity was observed with L-lactate dehydrogenase from Lactobacillus casei subsp. casei, with 69% identity. Therefore, its structure (PDB ID: 2ZQY:A was selected as a modelling template for homology modelling. Active residues are by sequence similarity predicted: S. thermophilus - HIS181 and S. aureus - HIS179. Binding energy of pyruvate to L-lactate dehydrogenase of S. thermopilus was - 7.874 kcal/mol. Pyruvate in L-lactate dehydrogenase of S. thermopilus makes H bonds with catalytic HIS181 (1.9 Å, as well as with THR235 (3.6 Å. Although our results indicate similar position of substrates between L-lactate dehydrogenase of S. thermopilus and S. aureus, differences in substrate distances and binding energy values could influence the reaction rate. Based on these results, the L-lactate dehydrogenase model proposed here could be used as a guide for further research, such as transition states of the reaction through molecular dynamics. [Projekat Ministarstva nauke Republike Srbije, br. III 46009

Natural plant hormones cytokinins increase stress resistance and longevity of Caenorhabditis elegans

NARCIS (Netherlands)

Kadlecová, Alena; Jirsa, Tomáš; Novák, Ondřej; Kammenga, Jan; Strnad, Miroslav; Voller, Jiří

2018-01-01

Cytokinins are phytohormones that are involved in many processes in plants, including growth, differentiation and leaf senescence. However, they also have various activities in animals. For example, kinetin and trans-zeatin can reduce levels of several aging markers in human fibroblasts. Kinetin

Cytokinin Dynamics during the Response to Nitrogen in Two Contrasting Plectranthus Genotypes

Czech Academy of Sciences Publication Activity Database

Paparozzi, E.T.; Chahal, J.K.; Dobrev, Petre; Claassen, E.A.; Stroup, W.W.; Vaňková, Radomíra

2016-01-01

Roč. 141, č. 3 (2016), s. 264-274 ISSN 0003-1062 Institutional support: RVO:61389030 Keywords : ZEATIN-TYPE CYTOKININS * ARABIDOPSIS-THALIANA * ABSCISIC-ACID Subject RIV: EF - Botanics Impact factor: 1.125, year: 2016 http://journal.ashspublications.org/content/141/3/264.abstract

Changes in Endogenous Cytokinins During Germination and Seedling Establishment of Tagetes minuta L.

Czech Academy of Sciences Publication Activity Database

Stirk, W.A.; Gold, J.D.; Novák, Ondřej; Strnad, Miroslav; van Staden, J.

2005-01-01

Roč. 47, č. 1 (2005), s. 1-7 ISSN 0167-6903 Institutional research plan: CEZ:AV0Z50380511 Keywords : Cytokinins * Germination * Seedling establishment Subject RIV: EF - Botanics Impact factor: 0.841, year: 2005

Fe(HSO4)3 as an Efficient Catalyst for Diazotization and Diazo Coupling Reactions

International Nuclear Information System (INIS)

Rahimizadeh, Mohammad; Eshghi, Hossein; Shiri, Ali; Ghadamyari, Zohreh; Matin, Maryam M.; Pordeli, Parvaneh; Oroojalian, Fatemeh

2012-01-01

Diazo coupling reactions of aromatic amines with 2-naphthol in a green, efficient and easy procedure is described. Ferric hydrogensulfate catalyses this reaction in water at room temperature and short reaction time with high yields. The antibacterial activities of the synthesized compounds against four pathogenic bacteria are also investigated

Kinetics and Mechanistic Study of the Ruthenium(III Catalysed Oxidative Decarboxylation of L-Proline by Alkaline Heptavalent Manganese (Stopped flow technique

Directory of Open Access Journals (Sweden)

R. S. Shettar

2005-01-01

Full Text Available The kinetics of ruthenium(III catalysed oxidation of L-Proline by permanganate in alkaline medium at a constant ionic strength has been studied spectrophotometrically using a rapid kinetic accessory. The reaction between permanganate and L-Proline in alkaline medium exhibits 2:1 stoichiometry (KMnO4: L-Proline. The reaction shows first order dependence on [permanganate] and [ruthenium(III] and apparent less than unit order dependence each in L-Proline and alkali concentrations. Reaction rate increases with increase in ionic strength and decrease in solvent polarity of the medium. Initial addition of reaction products did not affect the rate significantly. A mechanism involving the formation of a complex between catalyst and substrate has been proposed. The activation parameters were computed with respect to the slow step of the mechanism and discussed

Stress-induced cytokinin synthesis increases drought tolerance through the coordinated regulation of carbon and nitrogen assimilation in rice.

Science.gov (United States)

Reguera, Maria; Peleg, Zvi; Abdel-Tawab, Yasser M; Tumimbang, Ellen B; Delatorre, Carla A; Blumwald, Eduardo

2013-12-01

The effects of water deficit on carbon and nitrogen metabolism were investigated in flag leaves of wild-type and transgenic rice (Oryza sativa japonica 'Kitaake') plants expressing ISOPENTENYLTRANSFERASE (IPT; encoding the enzyme that mediates the rate-limiting step in cytokinin synthesis) under the control of P(SARK), a maturation- and stress-induced promoter. While the wild-type plants displayed inhibition of photosynthesis and nitrogen assimilation during water stress, neither carbon nor nitrogen assimilation was affected by stress in the transgenic P(SARK)::IPT plants. In the transgenic plants, photosynthesis was maintained at control levels during stress and the flag leaf showed increased sucrose (Suc) phosphate synthase activity and reduced Suc synthase and invertase activities, leading to increased Suc contents. The sustained carbon assimilation in the transgenic P(SARK)::IPT plants was well correlated with enhanced nitrate content, higher nitrate reductase activity, and sustained ammonium contents, indicating that the stress-induced cytokinin synthesis in the transgenic plants played a role in maintaining nitrate acquisition. Protein contents decreased and free amino acids increased in wild-type plants during stress, while protein content was preserved in the transgenic plants. Our results indicate that the stress-induced cytokinin synthesis in the transgenic plants promoted sink strengthening through a cytokinin-dependent coordinated regulation of carbon and nitrogen metabolism that facilitates an enhanced tolerance of the transgenic plants to water deficit.

Abscisic acid regulates root growth under osmotic stress conditions via an interacting hormonal network with cytokinin, ethylene and auxin.

Science.gov (United States)

Rowe, James H; Topping, Jennifer F; Liu, Junli; Lindsey, Keith

2016-07-01

Understanding the mechanisms regulating root development under drought conditions is an important question for plant biology and world agriculture. We examine the effect of osmotic stress on abscisic acid (ABA), cytokinin and ethylene responses and how they mediate auxin transport, distribution and root growth through effects on PIN proteins. We integrate experimental data to construct hormonal crosstalk networks to formulate a systems view of root growth regulation by multiple hormones. Experimental analysis shows: that ABA-dependent and ABA-independent stress responses increase under osmotic stress, but cytokinin responses are only slightly reduced; inhibition of root growth under osmotic stress does not require ethylene signalling, but auxin can rescue root growth and meristem size; osmotic stress modulates auxin transporter levels and localization, reducing root auxin concentrations; PIN1 levels are reduced under stress in an ABA-dependent manner, overriding ethylene effects; and the interplay among ABA, ethylene, cytokinin and auxin is tissue-specific, as evidenced by differential responses of PIN1 and PIN2 to osmotic stress. Combining experimental analysis with network construction reveals that ABA regulates root growth under osmotic stress conditions via an interacting hormonal network with cytokinin, ethylene and auxin. © 2016 The Authors. New Phytologist © 2016 New Phytologist Trust.

Copper-catalysed selective hydroamination reactions of alkynes

Science.gov (United States)

Shi, Shi-Liang; Buchwald, Stephen L.

2015-01-01

The development of selective reactions that utilize easily available and abundant precursors for the efficient synthesis of amines is a long-standing goal of chemical research. Despite the centrality of amines in a number of important research areas, including medicinal chemistry, total synthesis and materials science, a general, selective and step-efficient synthesis of amines is still needed. Here, we describe a set of mild catalytic conditions utilizing a single copper-based catalyst that enables the direct preparation of three distinct and important amine classes (enamines, α-chiral branched alkylamines and linear alkylamines) from readily available alkyne starting materials with high levels of chemo-, regio- and stereoselectivity. This methodology was applied to the asymmetric synthesis of rivastigmine and the formal synthesis of several other pharmaceutical agents, including duloxetine, atomoxetine, fluoxetine and tolterodine.

Efficient and selective N-alkylation of amines with alcohols catalysed by manganese pincer complexes

Science.gov (United States)

Elangovan, Saravanakumar; Neumann, Jacob; Sortais, Jean-Baptiste; Junge, Kathrin; Darcel, Christophe; Beller, Matthias

2016-01-01

Borrowing hydrogen (or hydrogen autotransfer) reactions represent straightforward and sustainable C–N bond-forming processes. In general, precious metal-based catalysts are employed for this effective transformation. In recent years, the use of earth abundant and cheap non-noble metal catalysts for this process attracted considerable attention in the scientific community. Here we show that the selective N-alkylation of amines with alcohols can be catalysed by defined PNP manganese pincer complexes. A variety of substituted anilines are monoalkylated with different (hetero)aromatic and aliphatic alcohols even in the presence of other sensitive reducible functional groups. As a special highlight, we report the chemoselective monomethylation of primary amines using methanol under mild conditions. PMID:27708259

Proline-catalysed asymmetric ketol cyclizations: The template ...

Indian Academy of Sciences (India)

Unknown

Abstract. A modified template mechanism based on modelling studies of energy minimised complexes is presented for the asymmetric proline-catalysed cyclization of triketones 1, 2 and 3 to the 2S,3S-ketols. 1a, 2a and 3a respectively. The template model involves a three-point contact as favoured in enzyme– substrate ...

Transgenic ipt tobacco overproducing cytokinins overaccumulates phenolic compounds during in vitro growth

Czech Academy of Sciences Publication Activity Database

Schnablová, Renáta; Synková, Helena; Vičánková, Anna; Burketová, Lenka; Eder, Josef; Cvikrová, Milena

2006-01-01

Roč. 44, - (2006), s. 526-534 ISSN 0981-9428 R&D Projects: GA ČR GA206/03/0310 Institutional research plan: CEZ:AV0Z50380511 Keywords : cytokinins * ipt * transgenic tobacco * in vitro cultivation Subject RIV: EF - Botanics Impact factor: 1.847, year: 2006

A Bacterial Receptor PcrK Senses the Plant Hormone Cytokinin to Promote Adaptation to Oxidative Stress

Directory of Open Access Journals (Sweden)

Fang-Fang Wang

2017-12-01

Full Text Available Summary: Recognition of the host plant is a prerequisite for infection by pathogenic bacteria. However, how bacterial cells sense plant-derived stimuli, especially chemicals that function in regulating plant development, remains completely unknown. Here, we have identified a membrane-bound histidine kinase of the phytopathogenic bacterium Xanthomonas campestris, PcrK, as a bacterial receptor that specifically detects the plant cytokinin 2-isopentenyladenine (2iP. 2iP binds to the extracytoplasmic region of PcrK to decrease its autokinase activity. Through a four-step phosphorelay, 2iP stimulation decreased the phosphorylation level of PcrR, the cognate response regulator of PcrK, to activate the phosphodiesterase activity of PcrR in degrading the second messenger 3′,5′-cyclic diguanylic acid. 2iP perception by the PcrK-PcrR remarkably improves bacterial tolerance to oxidative stress by regulating the transcription of 56 genes, including the virulence-associated TonB-dependent receptor gene ctrA. Our results reveal an evolutionarily conserved, inter-kingdom signaling by which phytopathogenic bacteria intercept a plant hormone signal to promote adaptation to oxidative stress. : How pathogenic bacteria use receptors to recognize the signals of the host plant is unknown. Wang et al. have identified a bacterial receptor histidine kinase that specifically senses the plant hormone cytokinin. Through a four-step phosphorelay, cytokinin perception triggers degradation of a second messenger, c-di-GMP, to activate the bacterial response to oxidative stress. Keywords: histidine kinase, ligand, cytokinin, autokinase activity, phosphorelay, response regulator, two-component signal transduction system, Xanthomonas campestris pv. campestris, virulence, oxidative stress

Co-ordinate regulation of cytokinin gene family members during flag leaf and reproductive development in wheat.

Science.gov (United States)

Song, Jiancheng; Jiang, Lijun; Jameson, Paula Elizabeth

2012-06-06

As the global population continues to expand, increasing yield in bread wheat is of critical importance as 20% of the world's food supply is sourced from this cereal. Several recent studies of the molecular basis of grain yield indicate that the cytokinins are a key factor in determining grain yield. In this study, cytokinin gene family members in bread wheat were isolated from four multigene families which regulate cytokinin synthesis and metabolism, the isopentenyl transferases (IPT), cytokinin oxidases (CKX), zeatin O-glucosyltransferases (ZOG), and β-glucosidases (GLU). As bread wheat is hexaploid, each gene family is also likely to be represented on the A, B and D genomes. By using a novel strategy of qRT-PCR with locus-specific primers shared among the three homoeologues of each family member, detailed expression profiles are provided of family members of these multigene families expressed during leaf, spike and seed development. The expression patterns of individual members of the IPT, CKX, ZOG, and GLU multigene families in wheat are shown to be tissue- and developmentally-specific. For instance, TaIPT2 and TaCKX1 were the most highly expressed family members during early seed development, with relative expression levels of up to 90- and 900-fold higher, respectively, than those in the lowest expressed samples. The expression of two cis-ZOG genes was sharply increased in older leaves, while an extremely high mRNA level of TaGLU1-1 was detected in young leaves. Key genes with tissue- and developmentally-specific expression have been identified which would be prime targets for genetic manipulation towards yield improvement in bread wheat breeding programmes, utilising TILLING and MAS strategies.

Effect of Cytokinin and Auxin Treatments on Morphogenesis, Terpenoid Biosynthesis, Photosystem Structural Organization, and Endogenous Isoprenoid Cytokinin Profile in Artemisia alba Turra In Vitro

Czech Academy of Sciences Publication Activity Database

Danova, K.; Motyka, Václav; Todorova, M.; Trendafilova, A.; Krumova, S.; Dobrev, Petre; Andreeva, T.; Oreshkova, T.; Taneva, S.; Evstatieva, L.

2018-01-01

Roč. 37, č. 2 (2018), s. 403-418 ISSN 0721-7595 R&D Projects: GA ČR(CZ) GA16-14649S Institutional support: RVO:61389030 Keywords : Artemisia alba Turra in vitro * Cis- and trans-zeatin * Endogenous cytokinins * Photosystem II and thylakoid morphology * Plant growth regulators * Terpenoid profile of the essential oil Subject RIV: EF - Botanics OBOR OECD: Plant sciences, botany Impact factor: 2.073, year: 2016

Understanding the Oxygen Reduction Reaction on a Y/Pt(111) Single Crystal

DEFF Research Database (Denmark)

Ulrikkeholm, Elisabeth Therese; Johansson, Tobias Peter; Malacrida, Paolo

2014-01-01

Polymer electrolyte membrane fuel cells (PEMFC) hold promise as a zero-emission source of power, particularly suitable for automotive vehicles. However, the high loading of Pt required to catalyse the oxygen reduction reaction (ORR) at the PEMFC cathode, prevents the commercialisation of this tec......Polymer electrolyte membrane fuel cells (PEMFC) hold promise as a zero-emission source of power, particularly suitable for automotive vehicles. However, the high loading of Pt required to catalyse the oxygen reduction reaction (ORR) at the PEMFC cathode, prevents the commercialisation...... using electrochemical measurements, low energy electron diffraction, ion scattering spectroscopy, angle resolved X-ray photoelectron spectroscopy, temperature programmed desorption of CO, and synchrotron based X-ray absorption spectroscopy and surface sensitive X-ray diffraction. These measurements were...

Stopped Flow Kinetics of MnII Catalysed Periodate Oxidation of 2, 3- dimethylaniline - Evaluation of Stability Constant of the Ternary Intermediate Complex

Directory of Open Access Journals (Sweden)

Rajneesh Dutt Kaushik

2015-03-01

Full Text Available The formation of ternary intermediate unstable complex during the oxidation of aromatic amines by periodate ion catalysed by MnII has been proposed in case of some anilines. This paper is the first report on stopped-flow kinetic study and evaluation of stability constant of ternary complex forming in the MnII - catalysed periodate oxidation of 2, 3-dimethylaniline (D in acetone-water medium. Stop-flow spectrophotometric method was used to study the ternary complex formation and to determine its stability constant. The stop-flow trace shows the reaction to occur in two steps. The first step, which is presumably the formation of ternary complex, is relatively fast while the second stage is relatively quite slow. The stability constant evaluated for D - MnII - IO4- ternary complex by determining  equilibrium absorbance is (2.2 ± 1.0 × 105. Kinetics of ternary complex formation was defined by the rate law(A  under pseudo first order conditions. ln{[C2]eq / ( [C2]eq -[C2]} = kobs . t (A where, kobs is the pseudo first order rate constant, [C2] is concentration of ternary complex at given time t, and [C2]eq is the equilibrium concentration of ternary complex. © 2015 BCREC UNDIP. All rights reservedReceived: 3rd October 2014; Revised: 4th December 2014; Accepted: 15th December 2014How to Cite: Kaushik, R.D., Agarwal, R., Tyagi, P., Singh, O., Singh, J. (2015. Stopped Flow Kinetics of MnII Catalysed Periodate Oxidation of 2,3-dimethylaniline - Evaluation of Stability Constant of the Ternary Intermediate Complex. Bulletin of Chemical Reaction Engineering & Catalysis, 10 (1: 78-87. (doi:10.9767/bcrec.10.1.7621.78-87Permalink/DOI: http://dx.doi.org/10.9767/bcrec.10.1.7621.78-87

Cytokinin profiling of long-term in vitro pea (Pisum sativum L.) shoot cultures

Czech Academy of Sciences Publication Activity Database

Plačková, Lenka; Hrdlička, Jakub; Smýkalová, I.; Cvečková, M.; Novák, Ondřej; Griga, M.; Doležal, Karel

2015-01-01

Roč. 77, č. 2 (2015), s. 125-132 ISSN 0167-6903 R&D Projects: GA MŠk(CZ) LO1204 Institutional support: RVO:61389030 Keywords : Cytokinins * Pea * Quantification Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 2.333, year: 2015

N9-Substituted N(6)-[(3-methylbut-2-en-1-yl)amino]purine derivatives and their biological activity in selected cytokinin bioassays

Czech Academy of Sciences Publication Activity Database

Mik, V.; Szüčová, Lucie; Spíchal, Lukáš; Plíhal, O.; Nisler, Jaroslav; Zahajská, L.; Doležal, Karel; Strnad, Miroslav

2011-01-01

Roč. 19, č. 23 (2011), s. 7244-7251 ISSN 0968-0896 R&D Projects: GA MŠk ED0007/01/01; GA ČR GA522/09/1576 Keywords : N6-[(3-Methylbut-2-en-1-yl)amino]purine * Isopentenyladenine derivatives * N9-Substituted derivatives * Cytokinins * Cytokinin receptors Subject RIV: EF - Botanics Impact factor: 2.921, year: 2011

A potential role for endogenous microflora in dormancy release, cytokinin metabolism and the response to fluridone in Lolium rigidum seeds.

Science.gov (United States)

Goggin, Danica E; Emery, R J Neil; Kurepin, Leonid V; Powles, Stephen B

2015-02-01

Dormancy in Lolium rigidum (annual ryegrass) seeds can be alleviated by warm stratification in the dark or by application of fluridone, an inhibitor of plant abscisic acid (ABA) biosynthesis via phytoene desaturase. However, germination and absolute ABA concentration are not particularly strongly correlated. The aim of this study was to determine if cytokinins of both plant and bacterial origin are involved in mediating dormancy status and in the response to fluridone. Seeds with normal or greatly decreased (by dry heat pre-treatment) bacterial populations were stratified in the light or dark and in the presence or absence of fluridone in order to modify their dormancy status. Germination was assessed and seed cytokinin concentration and composition were measured in embryo-containing or embryo-free seed portions. Seeds lacking bacteria were no longer able to lose dormancy in the dark unless supplied with exogenous gibberellin or fluridone. Although these seeds showed a dramatic switch from active cytokinin free bases to O-glucosylated storage forms, the concentrations of individual cytokinin species were only weakly correlated to dormancy status. However, cytokinins of apparently bacterial origin were affected by fluridone and light treatment of the seeds. It is probable that resident microflora contribute to dormancy status in L. rigidum seeds via a complex interaction between hormones of both plant and bacterial origin. This interaction needs to be taken into account in studies on endogenous seed hormones or the response of seeds to plant growth regulators. © The Author 2014. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Online UV-visible spectroscopy and multivariate curve resolution as powerful tool for model-free investigation of laccase-catalysed oxidation.

Science.gov (United States)

Kandelbauer, A; Kessler, W; Kessler, R W

2008-03-01

The laccase-catalysed transformation of indigo carmine (IC) with and without a redox active mediator was studied using online UV-visible spectroscopy. Deconvolution of the mixture spectra obtained during the reaction was performed on a model-free basis using multivariate curve resolution (MCR). Thereby, the time courses of educts, products, and reaction intermediates involved in the transformation were reconstructed without prior mechanistic assumptions. Furthermore, the spectral signature of a reactive intermediate which could not have been detected by a classical hard-modelling approach was extracted from the chemometric analysis. The findings suggest that the combined use of UV-visible spectroscopy and MCR may lead to unexpectedly deep mechanistic evidence otherwise buried in the experimental data. Thus, although rather an unspecific method, UV-visible spectroscopy can prove useful in the monitoring of chemical reactions when combined with MCR. This offers a wide range of chemists a cheap and readily available, highly sensitive tool for chemical reaction online monitoring.

An ethylene-induced regulatory module delays rose flower senescence by regulating cytokinin content

Science.gov (United States)

In many plant species, including rose (Rosa hybrida), flower senescence is promoted by the gaseous hormone, ethylene, and inhibited by cytokinin (CTK) class of hormones. However, the molecular mechanisms underlying these antagonistic effects are not well understood. In this current study, we charact...

Transition-state structure in the yeast alcohol dehydrogenase reaction: the magnitude of solvent and alpha-secondary hydrogen isotope effects

International Nuclear Information System (INIS)

Welsh, K.M.; Creighton, D.J.; Klinman, J.P.

1980-01-01

Solvent and alpha-secondary isotope effects have been measured in the yeast alcohol dehydrogenase reaction, under conditions of a rate-limiting transfer of hydrogen between coenzyme and substrate. Determination of catalytic constants in H20 and D20 as a function of pH(D) has allowed the separation of solvent effects on pKa from kcat. The small effect of D20 on pKa is tentatively assigned to ionization of an active-site ZnOH 2 . The near absence of an isotope effect on kcat in the direction of alcohol oxidation rules out a mechanism involving concerted catalysis by an active-site base of hydride transfer. The near identity of kinetic and equilibrium alpha-secondary isotope effects in the direction of alcohol oxidation implicates a transition-state structure which resembles aldehyde with regard to bond hybridization properties. The result contrasts sharply with previously reported structure - reactivity correlations, which implicate a transition-state structure resembling alcohol with regard to charge properties. The significance of these findings to the mechanism of NAD(P)H-dependent redox reactions is discussed

Fe(HSO{sub 4}){sub 3} as an Efficient Catalyst for Diazotization and Diazo Coupling Reactions

Energy Technology Data Exchange (ETDEWEB)

Rahimizadeh, Mohammad; Eshghi, Hossein; Shiri, Ali; Ghadamyari, Zohreh; Matin, Maryam M.; Pordeli, Parvaneh [Ferdowsi Univ. of Mashhad, Mashhad (Iran, Islamic Republic of); Oroojalian, Fatemeh [Univ. of Tehran, Tehran (Iran, Islamic Republic of)

2012-12-15

Diazo coupling reactions of aromatic amines with 2-naphthol in a green, efficient and easy procedure is described. Ferric hydrogensulfate catalyses this reaction in water at room temperature and short reaction time with high yields. The antibacterial activities of the synthesized compounds against four pathogenic bacteria are also investigated.

Interactions between abscisic acid and cytokinins during water stress and subsequent rehydration

Czech Academy of Sciences Publication Activity Database

Pospíšilová, Jana; Vágner, Martin; Malbeck, Jiří; Trávníčková, Alena; Baťková, Petra

2005-01-01

Roč. 49, - (2005), s. 533-540 ISSN 0006-3134 R&D Projects: GA ČR GA522/02/1099; GA AV ČR(CZ) IAA638105 Institutional research plan: CEZ:AV0Z50380511 Keywords : abscisic acid * cytokinins * water stress Subject RIV: EF - Botanics Impact factor: 0.792, year: 2005

Cytokinin response in pepper plants (Capsicum annuum L.) exposed to silver nanoparticles

Czech Academy of Sciences Publication Activity Database

Vinković, T.; Novák, Ondřej; Strnad, Miroslav; Goessler, W.; Jurašin, D. D.; Parađiković, N.; Vrček, I. V.

2017-01-01

Roč. 156, JUL (2017), s. 10-18 ISSN 0013-9351 R&D Projects: GA MŠk(CZ) LO1204 Institutional support: RVO:61389030 Keywords : Abiotic stress * Biodistribution * Cytokinin response * Pepper * Silver nanoparticles * Uptake Subject RIV: EB - Genetics ; Molecular Biology OBOR OECD: Plant sciences, botany Impact factor: 3.835, year: 2016

The role of the Saccharomyces cerevisiae lipoate protein ligase homologue, Lip3, in lipoic acid synthesis.

Science.gov (United States)

Hermes, Fatemah A; Cronan, John E

2013-10-01

The covalent attachment of lipoate to the lipoyl domains (LDs) of the central metabolism enzymes pyruvate dehydrogenase (PDH) and oxoglutarate dehydrogenase (OGDH) is essential for their activation and thus for respiratory growth in Saccharomyces cerevisiae. A third lipoate-dependent enzyme system, the glycine cleavage system (GCV), is required for utilization of glycine as a nitrogen source. Lipoate is synthesized by extraction of its precursor, octanoyl-acyl carrier protein (ACP), from the pool of fatty acid biosynthetic intermediates. Alternatively, lipoate is salvaged from previously modified proteins or from growth medium by lipoate protein ligases (Lpls). The first Lpl to be characterized, LplA of Escherichia coli, catalyses two partial reactions: activation of the acyl chain by formation of acyl-AMP, followed by transfer of the acyl chain to lipoyl domains (LDs). There is a surprising diversity within the Lpl family of enzymes, several of which catalyse reactions other than ligation reactions. For example, the Bacillus subtilis Lpl homologue LipM is an octanoyltransferase that transfers the octanoyl moiety from octanoyl-ACP to GCV. Another B. subtilis Lpl homologue, LipL, transfers octanoate from octanoyl-GCV to other LDs in an amido-transfer reaction. Study of eukaryotic Lpls has lagged behind studies of the bacterial enzymes. We report that the Lip3 Lpl homologue of the yeast S. cerevisiae has octanoyl-CoA-protein transferase activity, and discuss implications of this activity on the physiological role of Lip3 in lipoate synthesis. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

catalysed indolylation and pyrrolylation of isatins: Efficient synthesis ...

Indian Academy of Sciences (India)

Abstract. An efficient and cheap synthetic approach to 3,3-di(indolyl)oxindoles and 3,3-di(pyrrolyl) oxindoles has been developed via Zn(OTf)2 catalysed indolylation and pyrrolylation of isatins. A preliminary biochemical assay of the synthesized molecules in rodent models were performed to estimate the serum glutamate ...

Electrophilic aromatic substitution over zeolites generates Wheland-type reaction intermediates

NARCIS (Netherlands)

Chowdhury, Abhishek Dutta; Houben, Klaartje; Whiting, Gareth T.; Chung, Sangho; Baldus, Marc; Weckhuysen, Bert M.

2018-01-01

The synthesis of many industrial bulk and fine chemicals frequently involves electrophilic aromatic substitution (SEAr) reactions. The most widely practiced example of the SEAr mechanism is the zeolite-catalysed ethylation of benzene, using ethylene as an alkylating agent. However, the current

Viability, ultrastructure and cytokinin metabolism of free and immobilized tobacco chloroplasts

Czech Academy of Sciences Publication Activity Database

Polanská, Lenka; Vičánková, Anna; Dobrev, Petre; Macháčková, Ivana; Vaňková, Radomíra

2004-01-01

Roč. 26, č. 20 (2004), s. 1549-1555 ISSN 0141-5492 R&D Projects: GA MŠk OC 840.20; GA MŠk LN00A081; GA ČR GA206/03/0369 Institutional research plan: CEZ:AV0Z5038910 Keywords : calcium alginate * chloroplast ultrastructure * cytokinin metabolism Subject RIV: ED - Physiology Impact factor: 0.849, year: 2004

Metabolic production of a novel polymer feedstock, 3-carboxy muconate, from vanillin.

Science.gov (United States)

Gosling, Aaron; Fowler, S Jane; O'Shea, Michael S; Straffon, Melissa; Dumsday, Geoff; Zachariou, Michael

2011-04-01

Vanillin can be produced on a commercial scale by depolymerising renewable lignin. One product of microbial metabolism of vanillin by common soil microbes, such as Acinetobacter baylyi, is a tricarboxylic acid with a butadiene backbone known as 3-carboxy muconate (3CM). Three enzymes, 4-hydroxy benzaldehyde dehydrogenase, vanillate monooxygenase and protocatechuate 3,4-dioxygenase, catalyse the biotransformation of vanillin to 3CM. These three enzymes were metabolically engineered into an Escherichia coli host, giving a biocatalyst that converted vanillin into 3CM. The biocatalyst was found to give 100% yield of 3CM from 1 mM of vanillin after 39 h. The rate-limiting reaction was identified as the conversion of vanillate to 3,4-dihydroxybenzoate catalysed by vanillate monooxygenase. Low expression of the reductase subunit of this enzyme was identified as contributing to the reduced rate of this reaction. Proof of principle of a novel application for 3CM was demonstrated when it was converted into a trimethyl ester derivative and copolymerised with styrene.

Iron(III) porphyrin-catalysed oxidation reactions by m-chloro ...

Indian Academy of Sciences (India)

Unknown

The notable feature in this study is that none of the kinetic traces are expo- nential. A representative plot is given in figure 1 and the quantitative spectrum of TTBP• radical in dichloromethane is given in figure 2 (bold line). In this oxidation reaction under all the conditions, non-exponential kinetic traces were always obser-.

Silver nanoparticle catalysed redox reaction: An electron relay effect

International Nuclear Information System (INIS)

Mallick, Kaushik; Witcomb, Mike; Scurrell, Mike

2006-01-01

A silver cluster shows efficient catalytic activity in a redox reaction because the cluster acts as the electron relay centre behaving alternatively as an acceptor and as a donor of electrons. An effective transfer of electrons is possible when the redox potential of the cluster is intermediate between the electron donor and electron acceptor system

Diels-Alder reactions in confined spaces: the influence of catalyst structure and the nature of active sites for the retro-Diels-Alder reaction.

Science.gov (United States)

Cantín, Ángel; Gomez, M Victoria; de la Hoz, Antonio

2016-01-01

Diels-Alder cycloaddition between cyclopentadiene and p -benzoquinone has been studied in the confined space of a pure silica zeolite Beta and the impact on reaction rate due to the concentration effect within the pore and diffusion limitations are discussed. Introduction of Lewis or Brønsted acid sites on the walls of the zeolite strongly increases the reaction rate. However, contrary to what occurs with mesoporous molecular sieves (MCM-41), Beta zeolite does not catalyse the retro-Diels-Alder reaction, resulting in a highly selective catalyst for the cycloaddition reaction.

Pd(OAc)2/DPPF-catalysed microwave-assisted cyanides-free ...

Indian Academy of Sciences (India)

Pd(OAc)2/DPPF-catalysed microwave-assisted cyanides-free synthesis of aryl nitriles. DINESH N. SAWANT and BHALCHANDRA M. BHANAGE*. Department of Chemistry, Institute of Chemical Technology, N. Parekh Marg, Matunga,. Mumbai 400019 India. e-mail bm.bhanage@ictmumbai.edu.in. INDEX ...

Immobilization of alcohol dehydrogenase on ceramic silicon carbide membranes for enzymatic CH3 OH production

DEFF Research Database (Denmark)

Zeuner, Birgitte; Ma, Nicolaj; Berendt, Kasper

2018-01-01

BACKGROUND Alcohol dehydrogenase (ADH; EC 1.1.1.1) catalyzes oxidation of CH3OH to CHOH during NAD+ reduction to NADH. ADH can also accelerate the reverse reaction, which is studied as part of cascadic enzymatic conversion of CO2 to CH3OH. In the present study, immobilization of ADH onto macropor......BACKGROUND Alcohol dehydrogenase (ADH; EC 1.1.1.1) catalyzes oxidation of CH3OH to CHOH during NAD+ reduction to NADH. ADH can also accelerate the reverse reaction, which is studied as part of cascadic enzymatic conversion of CO2 to CH3OH. In the present study, immobilization of ADH onto......‐of‐concept for the use of NaOH‐treated SiC membranes for covalent enzyme immobilization and biocatalytic efficiency improvement of ADH during multiple reaction cycles. These data have implications for the development of robust extended enzymatic reactions....

The cytokinin response factors modulate root and shoot growth and promote leaf senescence in Arabidopsis

Czech Academy of Sciences Publication Activity Database

Raines, T.; Shanks, C.; Cheng, C.Y.; McPherson, D.; Argueso, C.T.; Kim, H.J.; Franco-Zorrilla, J.M.; Lopez-Vidriero, I.; Solano, R.; Vaňková, Radomíra; Schaller, G.E.; Kieber, J.J.

2016-01-01

Roč. 85, č. 1 (2016), s. 134-147 ISSN 0960-7412 Institutional support: RVO:61389030 Keywords : cytokinin * two-component signaling * transcription factors Subject RIV: EF - Botanics Impact factor: 5.901, year: 2016

Diurnal variation of cytokinin, auxin and abscisic acid levels in tobacco leaves

Czech Academy of Sciences Publication Activity Database

Nováková, Marie; Motyka, Václav; Dobrev, Petre; Malbeck, Jiří; Gaudinová, Alena

2005-01-01

Roč. 56, č. 421 (2005), s. 2877-2883 ISSN 0022-0957 R&D Projects: GA ČR GA206/03/0369; GA MŠk LN00A081 Institutional research plan: CEZ:AV0Z50380511 Keywords : abscisic acid * auxin * cytokinin Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.336, year: 2005

In vitro hydrogen production by glucose dehydrogenase and hydrogenase

Energy Technology Data Exchange (ETDEWEB)

Woodward, J. [Oak Ridge National Lab., TN (United States)

1996-10-01

A new in vitro enzymatic pathway for the generation of molecular hydrogen from glucose has been demonstrated. The reaction is based upon the oxidation of glucose by Thermoplasma acidophilum glucose dehydrogenase with the concomitant oxidation of NADPH by Pyrococcus furiosus hydrogenase. Stoichiometric yields of hydrogen were produced from glucose with continuous cofactor recycle. This simple system may provide a method for the biological production of hydrogen from renewable sources. In addition, the other product of this reaction, gluconic acid, is a high-value commodity chemical.

Palladium-catalysed direct cross-coupling of secondary alkyllithium reagents

NARCIS (Netherlands)

Vila, Carlos; Giannerini, Massimo; Hornillos, Valentin; Fananas-Mastral, Martin; Feringa, Ben L.

2014-01-01

Palladium-catalysed cross-coupling of secondary C(sp(3)) organometallic reagents has been a long-standing challenge in organic synthesis, due to the problems associated with undesired isomerisation or the formation of reduction products. Based on our recently developed catalytic C-C bond formation

Cytokinins in the perianth, carpels, and developing fruit of Helleborus niger L

Czech Academy of Sciences Publication Activity Database

Tarkowski, Petr; Tarkowská, Danuše; Novák, Ondřej; Mihaljević, S.; Magnus, V.; Strnad, Miroslav; Salopek-Sondi, N.

2006-01-01

Roč. 57, č. 10 (2006), s. 2237-2247 ISSN 0022-0957 Grant - others:Ministry of Science, Education, and Sports of the Republic of Croatia (HR) 0098080 Institutional research plan: CEZ:AV0Z50380511 Keywords : Christmas rose * cytokinin identification and quantification * fruit and seed development Subject RIV: CE - Biochemistry Impact factor: 3.630, year: 2006

Natural plant hormones cytokinins increase stress resistance and longevity of Caenorhabditis elegans

Czech Academy of Sciences Publication Activity Database

Kadlecová, Alena; Jirsa, Tomáš; Novák, Ondřej; Kammenga, J.; Strnad, Miroslav; Voller, J.

2018-01-01

Roč. 19, č. 2 (2018), s. 109-120 ISSN 1389-5729 R&D Projects: GA MŠk(CZ) LO1204; GA MŠk(CZ) LO1304 Institutional support: RVO:61389030 Keywords : Aging * Caenorhabditis elegans * Cytokinin * Kinetin * Phytohormones * Topolin * Zeatin Subject RIV: EB - Genetics ; Molecular Biology OBOR OECD: Plant sciences, botany Impact factor: 3.231, year: 2016

Antioxidant enzymatic protection during tobacco leaf ageing is affected by cytokinin depletion

Czech Academy of Sciences Publication Activity Database

Mýtinová, Zuzana; Motyka, Václav; Haisel, Daniel; Lubovská, Zuzana; Trávníčková, Alena; Dobrev, Petre; Holík, Josef; Wilhelmová, Naděžda

2011-01-01

Roč. 65, č. 1 (2011), s. 23-34 ISSN 0167-6903 R&D Projects: GA ČR GA522/03/0312; GA AV ČR IAA600380701; GA MŠk(CZ) LC06034 Institutional research plan: CEZ:AV0Z50380511 Keywords : Ageing * Antioxidant enzymes * Cytokinins Subject RIV: CE - Biochemistry Impact factor: 1.604, year: 2011

Terpenoid Profile of Artemisia Alba is Related to Endogenous Cytokinins in Vitro

Czech Academy of Sciences Publication Activity Database

Krumova, S.; Motyka, Václav; Dobrev, Petre; Todorova, M.; Trendafilova, A.; Evstatieva, L.; Danova, K.

2013-01-01

Roč. 19, č. 2 (2013), s. 26-30 ISSN 1310-0351 R&D Projects: GA ČR(CZ) GAP506/11/0774 Institutional research plan: CEZ:AV0Z50380511 Keywords : Artemisia alba * in vitro * endogenous cytokinins Subject RIV: EF - Botanics Impact factor: 0.136, year: 2012 http://www.agrojournal.org/19/02-06s.pdf

Kinetics of soil dehydrogenase in response to exogenous Cd toxicity

Energy Technology Data Exchange (ETDEWEB)

Tan, Xiangping [College of Natural Resources and Environment, Northwest A& F University, Yangling, 712100, Shaanxi (China); Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, CAS 723 Xingke Rd., Tianhe District, Guangzhou 510650 (China); Wang, Ziquan; Lu, Guannan [College of Natural Resources and Environment, Northwest A& F University, Yangling, 712100, Shaanxi (China); He, Wenxiang, E-mail: wenxianghe@nwafu.edu.cn [College of Natural Resources and Environment, Northwest A& F University, Yangling, 712100, Shaanxi (China); Key Laboratory of Plant Nutrition and Agro-environment in Northwest China, Ministry of Agriculture, Northwest A& F University, Yangling, 712100, Shaanxi (China); Wei, Gehong [College of Life Sciences, Northwest A& F University, Yangling, 712100, Shaanxi (China); Huang, Feng; Xu, Xinlan; Shen, Weijun [Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, CAS 723 Xingke Rd., Tianhe District, Guangzhou 510650 (China)

2017-05-05

Highlights: • pH explained 30–45% of the dehydrogenase activity (DHA), V{sub max}, and K{sub m} variations across soils. • Different inhibition mechanism of Cd to DHA varied soil types. • Soil properties and inhibition constant affect the toxicity of Cd. • Reaction constant (k) could indicate sensitively the toxicity of Cd to DHA. - Abstract: Soil dehydrogenase plays a role in the biological oxidation of soil organic matter and can be considered a good measure of the change of microbial oxidative activity under environmental pollutions. However, the kinetic characteristic of soil dehydrogenase under heavy metal stresses has not been investigated thoroughly. In this study, we characterized the kinetic characteristic of soil dehydrogenase in 14 soil types, and investigated how kinetic parameters changed under spiked with different concentrations of cadmium (Cd). The results showed that the K{sub m} and V{sub max} values of soil dehydrogenase was among 1.4–7.3 mM and 15.9–235.2 μM h{sup −1} in uncontaminated soils, respectively. In latosolic red soil and brown soil, the inhibitory kinetic mechanism of Cd to soil dehydrogenase was anticompetitive inhibition with inhibition constants (K{sub i}) of 12 and 4.7 mM, respectively; in other soils belonged to linear mixed inhibition, the values of K{sub i} were between 0.7–4.2 mM. Soil total organic carbon and K{sub i} were the major factors affecting the toxicity of Cd to dehydrogenase activity. In addition, the velocity constant (k) was more sensitive to Cd contamination compared to V{sub max} and K{sub m}, which was established as an early indicator of gross changes in soil microbial oxidative activity caused by Cd contamination.

Mechanistic aspects of Os(VIII) catalysed oxidation of loop diuretic ...

Indian Academy of Sciences (India)

furosemide by Ag(III) periodate complex in aqueous alkaline medium. SHWETA J .... Os(VIII) catalysed DPA oxidation, the order in [OH. −. ] ... Victoria-3170, Australia) connected to a rapid ..... follows. The furosemide, periodate and hydroxide ion.

Identification and characterisation of Aedes aegypti aldehyde dehydrogenases involved in pyrethroid metabolism.

Directory of Open Access Journals (Sweden)

Nongkran Lumjuan

Full Text Available Pyrethroid insecticides, especially permethrin and deltamethrin, have been used extensively worldwide for mosquito control. However, insecticide resistance can spread through a population very rapidly under strong selection pressure from insecticide use. The upregulation of aldehyde dehydrogenase (ALDH has been reported upon pyrethroid treatment. In Aedes aegypti, the increase in ALDH activity against the hydrolytic product of pyrethroid has been observed in DDT/permethrin-resistant strains. The objective of this study was to identify the role of individual ALDHs involved in pyrethroid metabolism.Three ALDHs were identified; two of these, ALDH9948 and ALDH14080, were upregulated in terms of both mRNA and protein levels in a DDT/pyrethroid-resistant strain of Ae. aegypti. Recombinant ALDH9948 and ALDH14080 exhibited oxidase activities to catalyse the oxidation of a permethrin intermediate, phenoxybenzyl aldehyde (PBald, to phenoxybenzoic acid (PBacid.ALDHs have been identified in association with permethrin resistance in Ae. aegypti. Characterisation of recombinant ALDHs confirmed the role of this protein in pyrethroid metabolism. Understanding the biochemical and molecular mechanisms of pyrethroid resistance provides information for improving vector control strategies.

Novel approaches for using dehydrogenases and ene-reductases for organic synthesis

NARCIS (Netherlands)

Gargiulo, S.

2015-01-01

Oxidation of alcohols is a reaction of major interest for organic chemistry. However, the most common chemical routes developed so far involve the use of toxic or hazardous reagents or catalysts that often lack good chemoselectivity. In this respect, alcohol dehydrogenases (ADHs) represent a very

Cytokinin-induced photomorphogenesis in dark-grown Arabidopsis: a proteomic analysis

Czech Academy of Sciences Publication Activity Database

Lochmanová, G.; Zdráhal, Z.; Konečná, H.; Koukalová, Š.; Malbeck, Jiří; Souček, Přemysl; Válková, M.; Kiran, N.S.; Brzobohatý, Břetislav

2008-01-01

Roč. 59, č. 13 (2008), s. 3705-3719 ISSN 0022-0957 R&D Projects: GA MŠk(CZ) LC06034; GA MŠk 1M06030; GA AV ČR IAA600040701; GA AV ČR IAA600040612 Institutional research plan: CEZ:AV0Z50040507; CEZ:AV0Z50040702; CEZ:AV0Z50380511 Keywords : Arabidopsis thaliana * cytokinin * 2D electrophoresis * photomorphogenesis * proteome Subject RIV: ED - Physiology Impact factor: 4.001, year: 2008

The role of auxin and cytokinin signalling in specifying the root architecture of Arabidopsis thaliana

KAUST Repository

Muraro, Daniele; Byrne, Helen; King, John; Bennett, Malcolm

2013-01-01

these hormones and their signalling pathways. In this paper, sub-cellular and multi-cellular mathematical models are developed to investigate how interactions between auxin and cytokinin influence the size and location of regions of division and differentiation

Lipase-catalysed acylation of starch and determination of the degree of substitution by methanolysis and GC

Science.gov (United States)

2010-01-01

Background Natural polysaccharides such as starch are becoming increasingly interesting as renewable starting materials for the synthesis of biodegradable polymers using chemical or enzymatic methods. Given the complexity of polysaccharides, the analysis of reaction products is challenging. Results Esterification of starch with fatty acids has traditionally been monitored by saponification and back-titration, but in our experience this method is unreliable. Here we report a novel GC-based method for the fast and reliable quantitative determination of esterification. The method was used to monitor the enzymatic esterification of different starches with decanoic acid, using lipase from Thermomyces lanuginosus. The reaction showed a pronounced optimal water content of 1.25 mL per g starch, where a degree of substitution (DS) of 0.018 was obtained. Incomplete gelatinization probably accounts for lower conversion with less water. Conclusions Lipase-catalysed esterification of starch is feasible in aqueous gel systems, but attention to analytical methods is important to obtain correct DS values. PMID:21114817

Lipase-catalysed acylation of starch and determination of the degree of substitution by methanolysis and GC

Directory of Open Access Journals (Sweden)

Hauer Bernhard

2010-11-01

Full Text Available Abstract Background Natural polysaccharides such as starch are becoming increasingly interesting as renewable starting materials for the synthesis of biodegradable polymers using chemical or enzymatic methods. Given the complexity of polysaccharides, the analysis of reaction products is challenging. Results Esterification of starch with fatty acids has traditionally been monitored by saponification and back-titration, but in our experience this method is unreliable. Here we report a novel GC-based method for the fast and reliable quantitative determination of esterification. The method was used to monitor the enzymatic esterification of different starches with decanoic acid, using lipase from Thermomyces lanuginosus. The reaction showed a pronounced optimal water content of 1.25 mL per g starch, where a degree of substitution (DS of 0.018 was obtained. Incomplete gelatinization probably accounts for lower conversion with less water. Conclusions Lipase-catalysed esterification of starch is feasible in aqueous gel systems, but attention to analytical methods is important to obtain correct DS values.

Enantioselective synthesis of almorexant via iridium-catalysed intramolecular allylic amidation

NARCIS (Netherlands)

Fananas Mastral, Martin; Teichert, Johannes F.; Fernandez-Salas, Jose Antonio; Heijnen, Dorus; Feringa, Ben L.

2013-01-01

An enantioselective synthesis of almorexant, a potent antagonist of human orexin receptors, is presented. The chiral tetrahydroisoquinoline core structure was prepared via iridium-catalysed asymmetric intramolecular allylic amidation. Further key catalytic steps of the synthesis include an oxidative

Direct Determination of Six Cytokinin Nucleotide Monophosphates in Coconut Flesh by Reversed-Phase Liquid Chromatography-Tandem Mass Spectrometry.

Science.gov (United States)

Cao, Zhao-Yun; Ma, You-Ning; Sun, Li-Hua; Mou, Ren-Xiang; Zhu, Zhi-Wei; Chen, Ming-Xue

2017-11-15

Coconut contains many uncharacterized cytokinins that have important physiological effects in plants and humans. In this work, a method based on liquid chromatography-tandem mass spectrometry was developed for identification and quantification of six cytokinin nucleotide monophosphates in coconut flesh. Excellent separation was achieved using a low-coverage C18 bonded-phase column with an acidic mobile phase, which greatly improved the retention of target compounds. To enable high-throughput analysis, a single-step solid-phase extraction using mixed-mode anion-exchange cartridges was employed for sample preparation. This proved to be an effective method to minimize matrix effects and ensure high selectivity. The limits of detection varied from 0.06 to 0.3 ng/mL, and the limits of quantification ranged from 0.2 to 1.0 ng/mL. The linearity was statistically verified over 2 orders of magnitude, giving a coefficient of determination (R 2 ) greater than 0.9981. The mean recoveries were from 81 to 108%; the intraday precision (n = 6) was less than 11%; and the interday precision (n = 11) was within 14%. The developed method was applied to the determination of cytokinin nucleotide monophosphates in coconut flesh samples, and four of them were successfully identified and quantified. The results showed that trans-zeatin riboside-5'-monophosphate was the dominant cytokinin, with a concentration of 2.7-34.2 ng/g, followed by N 6 -isopentenyladenosine-5'-monophosphate (≤12.9 ng/g), while the concentrations of cis-zeatin riboside-5'-monophosphate and dihydrozeatin riboside-5'-monophosphate were less than 2.2 and 4.9 ng/g, respectively.

Tobacco susceptibility to Potato virus Y-NTN infection is affected by grafting and endogenous cytokinin content

Czech Academy of Sciences Publication Activity Database

Spoustová, Petra; Hýsková, V.; Müller, Karel; Schnablová, Renáta; Ryšlavá, H.; Čeřovská, Noemi; Malbeck, Jiří; Cvikrová, Milena; Synková, Helena

2015-01-01

Roč. 235, JUN 2015 (2015), s. 25-36 ISSN 0168-9452 Institutional support: RVO:61389030 Keywords : Cytokinin * ipt gene * Antioxidant system Subject RIV: EF - Botanics Impact factor: 3.362, year: 2015

Post-irradiation repairing processes of glucose-6-phosphate dehydrogenase and catalase from Hansenula Polymorpha yeast

International Nuclear Information System (INIS)

Postolache, Carmen; Postolache, Cristian; Dinu, Diana; Dinischiotu, Anca; Sahini, Victor Emanuel

2002-01-01

The post-irradiation repairing mechanisms of two Hansenula Polymorpha yeast enzymes, glucose-6-phosphate dehydrogenase and catalase, were studied. The kinetic parameters of the selected enzymes were investigated over one month since the moment of γ-irradiation with different doses in the presence of oxygen. Dose dependent decrease of initial reaction rates was noticed for both enzymes. Small variation of initial reaction rate was recorded for glucose-6-phosphate dehydrogenase over one month, with a decreasing tendency. No significant electrophoretic changes of molecular forms of this enzyme were observed after irradiation. Continuous strong decrease of catalase activity was evident for the first 20 days after irradiation. Partial recovery process of the catalytic activity was revealed by this study. (authors)

Endogenous cytokinins in Cocos nucifera L. in vitro cultures obtained from plumular explants

Czech Academy of Sciences Publication Activity Database

Sáenz, L.; Azpeitia, A.; Oropeza, C.; Jones, L.; Fuchsová, Květoslava; Spíchal, Lukáš; Strnad, Miroslav

2010-01-01

Roč. 29, č. 11 (2010), s. 1227-1234 ISSN 0721-7714 R&D Projects: GA ČR GA301/08/1649; GA AV ČR IBS5038351 Institutional research plan: CEZ:AV0Z50380511 Keywords : Coconut palm * Somatic embryogenesis * Endogenous cytokinins Subject RIV: EF - Botanics Impact factor: 2.279, year: 2010

A more robust model of the biodiesel reaction, allowing identification of process conditions for significantly enhanced rate and water tolerance.

Science.gov (United States)

Eze, Valentine C; Phan, Anh N; Harvey, Adam P

2014-03-01

A more robust kinetic model of base-catalysed transesterification than the conventional reaction scheme has been developed. All the relevant reactions in the base-catalysed transesterification of rapeseed oil (RSO) to fatty acid methyl ester (FAME) were investigated experimentally, and validated numerically in a model implemented using MATLAB. It was found that including the saponification of RSO and FAME side reactions and hydroxide-methoxide equilibrium data explained various effects that are not captured by simpler conventional models. Both the experiment and modelling showed that the "biodiesel reaction" can reach the desired level of conversion (>95%) in less than 2min. Given the right set of conditions, the transesterification can reach over 95% conversion, before the saponification losses become significant. This means that the reaction must be performed in a reactor exhibiting good mixing and good control of residence time, and the reaction mixture must be quenched rapidly as it leaves the reactor. Copyright © 2014 Elsevier Ltd. All rights reserved.

O-Glucosylation of cis-Zeatin in Maize. Characterization of Genes, Enzymes, and Endogenous Cytokinins

Czech Academy of Sciences Publication Activity Database

Veach, Y. K.; Martin, R. C.; Mok, D. W. S.; Malbeck, Jiří; Vaňková, Radomíra; Mok, M. C.

2003-01-01

Roč. 131, č. 3 (2003), s. 1374-1380 ISSN 0032-0889 R&D Projects: GA MŠk ME 406 Institutional research plan: CEZ:AV0Z5038910 Keywords : Cis-cytokinin * O-glucosylation * Zea Mays Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 5.634, year: 2003

Evidence for catabolite degradation in the glucose-dependent inactivation of yeast cytoplasmic malate dehydrogenase

International Nuclear Information System (INIS)

Neeff, J.; Haegele, E.; Nauhaus, J.; Heer, U.; Mecke, D.

1978-01-01

The cytoplasmic malate dehydrogenase of Saccharomyces cerevisiae was radioactively labeled during its synthesis on a glucose-free derepression medium. After purification a sensitive radioimmunoassay for this enzyme could be developed. The assay showed that after the physiological, glucose-dependent 'catabolite inactivation' of cytoplasmic malate dehydrogenase an inactive enzyme protein is immunologically not detectable. Together with the irreversibility of this reaction in vivo this finding strongly suggests a proteolytic mechanism of enzyme inactivation. For this process the term 'catabolite degradation' is used. (orig.) [de

Evaluation of Relationship Between Auxin and Cytokinine Hormones on Yield and Yield Components of Maize under Drought Stress Condition

Directory of Open Access Journals (Sweden)

A Mahrokh

2016-10-01

Full Text Available Introduction Drought is one of the major environmental conditions that adversely affects plant growth and crop yield. In the face of a global scarcity of water resources, water stress has already become a primary factor in limiting crop production worldwide. Drought is the major restriction in maize production. The plant growth reduction under drought stress conditions could be an outcome of altered hormonal balance and hence the exogenous application of growth regulators under stress conditions could be the possible means for reversing the effects of abiotic stress. Phytohormones such as auxine and cytokinine are known to be involved in the regulation of plant response to the adverse effects of stress conditions. Previous studies have shown that endogenous hormones are essential regulators for translocation and partitioning of photoassimilates for grain filling in cereal crops, and therefore could be involved in the regulation of grain weight and yield. Materials and Methods The experiment was carried out in three separately environments included non-drought stress environment (irrigation after soil moisture reached to 75% field capacity, drought stress in vegetative stage (irrigation after soil moisture reached to 50% field capacity in V4 to tasseling stage, but irrigation after soil moisture reached to 75% field capacity in pollination to physiological maturity stage and drought stress in reproductive stage (irrigation after soil moisture reached to 75% field capacity in V4 to tasseling stage and irrigation after soil moisture reached to 50% field capacity in pollination to physiological maturity stage. Cytokinin hormone in three levels (control, spraying in V5 –V6 and V8-V10 stages and auxin hormone in three levels (control, spraying in silk emergence stage and 15 days after that were laid out as a factorial design based on randomized complete block with three replications in each environment at Seed and Plant Improvement Institute (SPII

Remodeling of Cytokinin Metabolism at Infection Sites of Colletotrichum graminicola on Maize Leaves

Czech Academy of Sciences Publication Activity Database

Behr, M.; Motyka, Václav; Weihmann, F.; Malbeck, Jiří; Deising, H. B.; Wirsel, S. G. R.

2012-01-01

Roč. 25, č. 8 (2012), s. 1073-1082 ISSN 0894-0282 R&D Projects: GA ČR(CZ) GAP506/11/0774; GA MŠk(CZ) LC06034 Institutional research plan: CEZ:AV0Z50380511 Keywords : Colletotrichum graminicola * maize * cytokinin Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 4.307, year: 2012

Two Cytokinin Receptors of Arabidopsis thaliana, CRE1/AHK4 and AHK3, Differ in their Ligand Specificity in a Bacterial Assay

Czech Academy of Sciences Publication Activity Database

Spíchal, Lukáš; Rakova, N. Y.; Riefler, M.; Romanov, G. A.; Strnad, Miroslav; Schmülling, T.

2004-01-01

Roč. 45, č. 9 (2004), s. 1299-1305 ISSN 0032-0781 R&D Projects: GA MŠk LZ1K03021 Grant - others:Deutsche Forschungsgemeinschaft(DE) Schm 814/13-2; VW Stiftung(DE) I/76865; Russian Foundation of Basic Research(RU) NN 01-04-04002/103-04-04001; NATO(US) LST-EV977817 Institutional research plan: CEZ:AV0Z5038910 Keywords : Arabidopsis thaliana * cytokinin * cytokinin receptor Subject RIV: ED - Physiology Impact factor: 3.258, year: 2004

Micro-coulometric study of bioelectrochemical reaction coupled with TCA cycle.

Science.gov (United States)

Tsujimura, Seiya; Fukuda, Jun; Shirai, Osamu; Kano, Kenji; Sakai, Hideki; Tokita, Yuichi; Hatazawa, Tsuyonobu

2012-04-15

The mediated electro-enzymatic electrolysis systems based on the tricarboxylic acid (TCA) cycle reaction were examined on a micro-bulk electrolytic system. A series of the enzyme-catalyzed reactions in the TCA cycle was coupled with electrode reaction. Electrochemical oxidation of NADH was catalyzed by diaphorase with an aid of a redox mediator with a formal potential of -0.15 V vs. Ag|AgCl. The mediator was also able to shuttle electrons between succinate dehydrogenase and electrode. The charge during the electrolysis increased on each addition of dehydrogenase reaction in a cascade of the TCA cycle. However, the electrolysis efficiencies were close to or less than 90% because of the product inhibition. Lactate oxidation to acetyl-CoA catalyzed by two NAD-dependent dehydrogenases was coupled with the bioelectrochemical TCA cycle reaction to achieve the 12-electron oxidation of lactate to CO(2). The charge passed in the bioelectrocatalytic oxidation of 5 nmol of lactate was 4 mC, which corresponds to 70% of the electrolysis efficiency. Copyright © 2012 Elsevier B.V. All rights reserved.

Cytokinin-induced VvTFL1A expression may be involved in the control of grapevine fruitfulness

Czech Academy of Sciences Publication Activity Database

Crane, O.; Halaly, T.; Pang, X.; Lavee, S.; Perl, A.; Vaňková, Radomíra; Or, E.

2012-01-01

Roč. 235, č. 1 (2012), s. 181-192 ISSN 0032-0935 Institutional research plan: CEZ:AV0Z50380511 Keywords : Cytokinin * Floral development * Fruitfulness Subject RIV: ED - Physiology Impact factor: 3.347, year: 2012

Pyruvate Dehydrogenase and Pyruvate Dehydrogenase Kinase Expression in Non Small Cell Lung Cancer and Tumor-Associated Stroma

Directory of Open Access Journals (Sweden)

Michael I. Koukourakis

2005-01-01

Full Text Available Pyruvate dehydrogenase (PDH catalyzes the conversion of pyruvate to acetyl-coenzyme A, which enters into the Krebs cycle, providing adenosine triphosphate (ATP to the cell. PDH activity is under the control of pyruvate dehydrogenase kinases (PDKs. Under hypoxic conditions, conversion of pyruvate to lactate occurs, a reaction catalyzed by lactate dehydrogenase 5 (LDH5. In cancer cells, however, pyruvate is transformed to lactate occurs, regardless of the presence of oxygen (aerobic glycolysis/Warburg effect. Although hypoxic intratumoral conditions account for HIFia stabilization and induction of anaerobic metabolism, recent data suggest that high pyruvate concentrations also result in HIFia stabilization independently of hypoxia. In the present immunohistochemical study, we provide evidence that the PDH/PDK pathway is repressed in 73% of non small cell lung carcinomas, which may be a key reason for HIFia stabilization and “aerobic glycolysis.” However, about half of PDHdeficient carcinomas are not able to switch on the HIF pathway, and patients harboring these tumors have an excellent postoperative outcome. A small subgroup of clinically aggressive tumors maintains a coherent PDH and HIF/LDH5 expression. In contrast to cancer cells, fibroblasts in the tumor-supporting stroma exhibit an intense PDH but reduced PDK1 expression favoring maximum PDH activity. This means that stroma may use lactic acid produced by tumor cells, preventing the creation of an intolerable intratumoral acidic environment at the same time.

Methyl jasmonate down-regulates endogenous cytokinin levels in cotyledons of Cucurbita pepo (zucchini) seedlings

Czech Academy of Sciences Publication Activity Database

Ananieva, H.; Malbeck, Jiří; Kamínek, Miroslav; Staden, J.

2004-01-01

Roč. 122, č. 4 (2004), s. 496-503 ISSN 0031-9317 R&D Projects: GA ČR GA522/02/0530 Institutional research plan: CEZ:AV0Z5038910 Keywords : methyl jasmonate * senescence * cytokinin Subject RIV: GD - Fertilization, Irrigation, Soil Processing Impact factor: 2.017, year: 2004

Analysis of 2-methylthio-derivatives of isoprenoid cytokinins by liquid chromatography-tandem mass spectrometry

Czech Academy of Sciences Publication Activity Database

Tarkowski, Petr; Václavíková, Kateřina; Novák, Ondřej; Pertry, I.; Hanuš, Jan; Whenham, R.; Vereecke, D.; Šebela, M.; Strnad, Miroslav

2010-01-01

Roč. 680, 1-2 (2010), s. 86-91 ISSN 0003-2670 R&D Projects: GA ČR GA301/08/1649 Institutional research plan: CEZ:AV0Z50380511 Keywords : Cytokinins * Rhodococcus fascians * High-performance liquid chromatography Subject RIV: CE - Biochemistry Impact factor: 4.310, year: 2010

Structure of d-3-hydroxybutyrate dehydrogenase prepared in the presence of the substrate d-3-hydroxybutyrate and NAD+

International Nuclear Information System (INIS)

Hoque, Md Mominul; Shimizu, Satoru; Juan, Ella Czarina Magat; Sato, Yoshiteru; Hossain, Md Tofazzal; Yamamoto, Tamotsu; Imamura, Shigeyuki; Suzuki, Kaoru; Amano, Hitoshi; Sekiguchi, Takeshi; Tsunoda, Masaru; Takénaka, Akio

2009-01-01

The crystal structure of A. faecalisd-3-hydroxybutyrate dehydrogenase prepared in the presence of d-3-hydroxybutyrate and NAD + reveals the substrate/product-binding geometry as the first example which suggests that the catalytic reaction occurs by shuttle movements of a hydrogen negative ion from the substrate to NAD + and from NADH to the product. d-3-Hydroxybutyrate dehydrogenase from Alcaligenes faecalis catalyzes the reversible conversion between d-3-hydroxybutyrate and acetoacetate. The enzyme was crystallized in the presence of the substrate d-3-hydroxybutyrate and the cofactor NAD + at the optimum pH for the catalytic reaction. The structure, which was solved by X-ray crystallography, is isomorphous to that of the complex with the substrate analogue acetate. The product as well as the substrate molecule are accommodated well in the catalytic site. Their binding geometries suggest that the reversible reactions occur by shuttle movements of a hydrogen negative ion from the C3 atom of the substrate to the C4 atom of NAD + and from the C4 atom of NADH to the C3 atom of the product. The reaction might be further coupled to the withdrawal of a proton from the hydroxyl group of the substrate by the ionized Tyr155 residue. These structural features strongly support the previously proposed reaction mechanism of d-3-hydroxybutyrate dehydrogenase, which was based on the acetate-bound complex structure

A conserved residue of l-alanine dehydrogenase from Bacillus pseudofirmus, Lys-73, participates in the catalytic reaction through hydrogen bonding.

Science.gov (United States)

He, Guangzheng; Xu, Shujing; Wang, Shanshan; Zhang, Qing; Liu, Dong; Chen, Yuling; Ju, Jiansong; Zhao, Baohua

2018-03-01

A multiple protein sequence alignment of l-alanine dehydrogenases from different bacterial species revealed that five highly conserved amino acid residues Arg-15, Lys-73, Lys-75, His-96 and Asp-269 are potential catalytic residues of l-alanine dehydrogenase from Bacillus pseudofirmus OF4. In this study, recombinant OF4Ald and its mutants of five conserved residues were constructed, expressed in Escherichia coli, purified by His 6 -tag affinity column and gel filtration chromatography, structure homology modeling, and characterized. The purified protein OF4Ald displayed high specificity to l-alanine (15Umg -1 ) with an optimal temperature and pH of 40°C and 10.5, respectively. Enzymatic assay and activity staining in native gels showed that mutations at four conserved residue Arg-15, Lys-75, His-96 and Asp-269 (except residue Lys-73) resulted in a complete loss in enzymatic activity, which signified that these predicted active sites are indispensable for OF4Ald activity. In contrast, the mutant K73A resulted in 6-fold improvement in k cat /K m towards l-alanine as compared to the wild type protein. Further research of the residue Lys-73 substituted by various amino acids and structural modeling revealed that residue Lys-73 might be involved in the catalytic reaction of the enzyme by influencing the enzyme-substrate binding through the hydrogen-bonding interaction with conserved residue Lys-75. Copyright © 2017 Elsevier Inc. All rights reserved.

Stress-Induced Cytokinin Synthesis Increases Drought Tolerance through the Coordinated Regulation of Carbon and Nitrogen Assimilation in Rice1[C][W][OPEN

Science.gov (United States)

Reguera, Maria; Peleg, Zvi; Abdel-Tawab, Yasser M.; Tumimbang, Ellen B.; Delatorre, Carla A.; Blumwald, Eduardo

2013-01-01

The effects of water deficit on carbon and nitrogen metabolism were investigated in flag leaves of wild-type and transgenic rice (Oryza sativa japonica ‘Kitaake’) plants expressing ISOPENTENYLTRANSFERASE (IPT; encoding the enzyme that mediates the rate-limiting step in cytokinin synthesis) under the control of PSARK, a maturation- and stress-induced promoter. While the wild-type plants displayed inhibition of photosynthesis and nitrogen assimilation during water stress, neither carbon nor nitrogen assimilation was affected by stress in the transgenic PSARK::IPT plants. In the transgenic plants, photosynthesis was maintained at control levels during stress and the flag leaf showed increased sucrose (Suc) phosphate synthase activity and reduced Suc synthase and invertase activities, leading to increased Suc contents. The sustained carbon assimilation in the transgenic PSARK::IPT plants was well correlated with enhanced nitrate content, higher nitrate reductase activity, and sustained ammonium contents, indicating that the stress-induced cytokinin synthesis in the transgenic plants played a role in maintaining nitrate acquisition. Protein contents decreased and free amino acids increased in wild-type plants during stress, while protein content was preserved in the transgenic plants. Our results indicate that the stress-induced cytokinin synthesis in the transgenic plants promoted sink strengthening through a cytokinin-dependent coordinated regulation of carbon and nitrogen metabolism that facilitates an enhanced tolerance of the transgenic plants to water deficit. PMID:24101772

Tissue- and Cell-Specific Cytokinin Activity in Populus × canescens Monitored by ARR5::GUS Reporter Lines in Summer and Winter.

Science.gov (United States)

Paul, Shanty; Wildhagen, Henning; Janz, Dennis; Teichmann, Thomas; Hänsch, Robert; Polle, Andrea

2016-01-01

Cytokinins play an important role in vascular development. But knowledge on the cellular localization of this growth hormone in the stem and other organs of woody plants is lacking. The main focus of this study was to investigate the occurrence and cellular localization of active cytokinins in leaves, roots, and along the stem of Populus × canescens and to find out how the pattern is changed between summer and winter. An ARR5::GUS reporter construct was used to monitor distribution of active cytokinins in different tissues of transgenic poplar lines. Three transgenic lines tested under outdoor conditions showed no influence of ARR5::GUS reporter construct on the growth performance compared with the wild-type, but one line lost the reporter activity. ARR5::GUS activity indicated changes in the tissue- and cell type-specific pattern of cytokinin activity during dormancy compared with the growth phase. ARR5::GUS activity, which was present in the root tips in the growing season, disappeared in winter. In the stem apex ground tissue, ARR5::GUS activity was higher in winter than in summer. Immature leaves from tissue-culture grown plants showed inducible ARR5::GUS activity. Leaf primordia in summer showed ARR5::GUS activity, but not the expanded leaves of outdoor plants or leaf primordia in winter. In stem cross sections, the most prominent ARR5::GUS activity was detected in the cortex region and in the rays of bark in summer and in winter. In the cambial zone the ARR5::GUS activity was more pronounced in the dormant than in growth phase. The pith and the ray cells adjacent to the vessels also displayed ARR5::GUS activity. In silico analyses of the tissue-specific expression patterns of the whole PtRR type-A family of poplar showed that PtRR10, the closest ortholog to the Arabidopsis ARR5 gene, was usually the most highly expressed gene in all tissues. In conclusion, gene expression and tissue-localization indicate high activity of cytokinins not only in summer, but

Mechanism and Stereoselectivity of Zeolite-catalysed Sugar Isomerisation in Alcohols

DEFF Research Database (Denmark)

Shunmugavel, Saravanamurugan; Riisager, Anders; Taarning, Esben

2016-01-01

Glucose isomerisation to fructose can occur by different pathways and the mechanism of zeolite-catalysed glucose isomerisation in methanol has remained incompletely understood. Herein, the mechanism is studied using an 1H-13C HSQC NMR assay resolving different fructose isotopomers. We find that z...

Cytokinin-induced activity of antioxidant enzymes in transgenic Pssu-ipt tobacco during plant ontogeny

Czech Academy of Sciences Publication Activity Database

Synková, Helena; Semorádová, Šárka; Schnablová, Renáta; Witters, E.; Hušák, M.; Valcke, R.

2006-01-01

Roč. 50, - (2006), s. 31-41 ISSN 0006-3134 R&D Projects: GA ČR GA206/01/1061; GA ČR GA206/03/0310 Institutional research plan: CEZ:AV0Z50380511 Keywords : cytokinins * antioxidant enzymes * ontogenesis Subject RIV: CE - Biochemistry Impact factor: 1.198, year: 2006

Changes in cytokinin and auxin concentrations in seaweed concentrates when stored at an elevated temperature

Czech Academy of Sciences Publication Activity Database

Stirk, W. A.; Arthur, G. D.; Lourens, A. F.; Novák, Ondřej; Strnad, Miroslav; van Staden, J.

2004-01-01

Roč. 16, č. 1 (2004), s. 31-39 ISSN 0022-3646 R&D Projects: GA ČR GA522/03/0323 Institutional research plan: CEZ:AV0Z5038910 Keywords : accelerated storage * auxins * cytokinins Subject RIV: EF - Botanics Impact factor: 2.490, year: 2004

Multimetallic catalysed cross-coupling of aryl bromides with aryl triflates

Science.gov (United States)

Ackerman, Laura K. G.; Lovell, Matthew M.; Weix, Daniel J.

2015-08-01

The advent of transition-metal catalysed strategies for forming new carbon-carbon bonds has revolutionized the field of organic chemistry, enabling the efficient synthesis of ligands, materials, and biologically active molecules. In cases where a single metal fails to promote a selective or efficient transformation, the synergistic cooperation of two distinct catalysts--multimetallic catalysis--can be used instead. Many important reactions rely on multimetallic catalysis, such as the Wacker oxidation of olefins and the Sonogashira coupling of alkynes with aryl halides, but this approach has largely been limited to the use of metals with distinct reactivities, with only one metal catalyst undergoing oxidative addition. Here, we demonstrate that cooperativity between two group 10 metal catalysts--(bipyridine)nickel and (1,3-bis(diphenylphosphino)propane)palladium--enables a general cross-Ullmann reaction (the cross-coupling of two different aryl electrophiles). Our method couples aryl bromides with aryl triflates directly, eliminating the use of arylmetal reagents and avoiding the challenge of differentiating between multiple carbon-hydrogen bonds that is required for direct arylation methods. Selectivity can be achieved without an excess of either substrate and originates from the orthogonal reactivity of the two catalysts and the relative stability of the two arylmetal intermediates. While (1,3-bis(diphenylphosphino)propane)palladium reacts preferentially with aryl triflates to afford a persistent intermediate, (bipyridine)nickel reacts preferentially with aryl bromides to form a transient, reactive intermediate. Although each catalyst forms less than 5 per cent cross-coupled product in isolation, together they are able to achieve a yield of up to 94 per cent. Our results reveal a new method for the synthesis of biaryls, heteroaryls, and dienes, as well as a general mechanism for the selective transfer of ligands between two metal catalysts. We anticipate that this

Nitrate modulates stem cell dynamics in Arabidopsis shoot meristems through cytokinins

OpenAIRE

Jonsson, Sten Henrik; Meyerowitz,; Landrein, Benoit Pierre; Formosa-Jordan,; Malivert,; Schuster, C; Melnyk, CW; Yang, W; Turnbull,; Locke, James Charles

2018-01-01

The shoot apical meristem (SAM) is responsible for the generation of all of the aerial parts of plants. Given its critical role, dynamical changes in SAM activity should play a central role in the adaptation of plant architecture to the environment. Using quantitative microscopy, grafting experiments and genetic perturbations, we connect the plant environment to the SAM, by describing the molecular mechanism by which cytokinins signal the level of nutrient availability to the SAM. We show tha...

Structural and kinetic basis for substrate selectivity in Populus tremuloides sinapyl alcohol dehydrogenase.

Science.gov (United States)

Bomati, Erin K; Noel, Joseph P

2005-05-01

We describe the three-dimensional structure of sinapyl alcohol dehydrogenase (SAD) from Populus tremuloides (aspen), a member of the NADP(H)-dependent dehydrogenase family that catalyzes the last reductive step in the formation of monolignols. The active site topology revealed by the crystal structure substantiates kinetic results indicating that SAD maintains highest specificity for the substrate sinapaldehyde. We also report substantial substrate inhibition kinetics for the SAD-catalyzed reduction of hydroxycinnamaldehydes. Although SAD and classical cinnamyl alcohol dehydrogenases (CADs) catalyze the same reaction and share some sequence identity, the active site topology of SAD is strikingly different from that predicted for classical CADs. Kinetic analyses of wild-type SAD and several active site mutants demonstrate the complexity of defining determinants of substrate specificity in these enzymes. These results, along with a phylogenetic analysis, support the inclusion of SAD in a plant alcohol dehydrogenase subfamily that includes cinnamaldehyde and benzaldehyde dehydrogenases. We used the SAD three-dimensional structure to model several of these SAD-like enzymes, and although their active site topologies largely mirror that of SAD, we describe a correlation between substrate specificity and amino acid substitution patterns in their active sites. The SAD structure thus provides a framework for understanding substrate specificity in this family of enzymes and for engineering new enzyme specificities.

Opposite roles of the Arabidopsis cytokinin receptors AHK2 and AHK3 in the expression of plastid genes and genes for the plastid transcriptional machinery during senescence.

Science.gov (United States)

Danilova, Maria N; Kudryakova, Natalia V; Doroshenko, Anastasia S; Zabrodin, Dmitry A; Rakhmankulova, Zulfira F; Oelmüller, Ralf; Kusnetsov, Victor V

2017-03-01

Cytokinin membrane receptors of the Arabidopsis thaliana AHK2 and AHK3 play opposite roles in the expression of plastid genes and genes for the plastid transcriptional machinery during leaf senescence Loss-of-function mutants of Arabidopsis thaliana were used to study the role of cytokinin receptors in the expression of chloroplast genes during leaf senescence. Accumulation of transcripts of several plastid-encoded genes is dependent on the АНК2/АНК3 receptor combination. АНК2 is particularly important at the final stage of plant development and, unlike АНК3, a positive regulator of leaf senescence. Cytokinin-dependent up-regulation of the nuclear encoded genes for chloroplast RNA polymerases RPOTp and RPOTmp suggests that the hormone controls plastid gene expression, at least in part, via the expression of nuclear genes for the plastid transcription machinery. This is further supported by cytokinin dependent regulation of genes for the nuclear encoded plastid σ-factors, SIG1-6, which code for components of the transcriptional apparatus in chloroplasts.

Quantitative analysis of cytokinins in plants by liquid chromatography single-quadrupole mass spectrometry

Czech Academy of Sciences Publication Activity Database

Novák, Ondřej; Tarkowski, Petr; Tarkowská, Danuše; Doležal, Karel; Lenobel, René; Strnad, Miroslav

2003-01-01

Roč. 480, č. 2 (2003), s. 207ů218 ISSN 0003-2670 R&D Projects: GA ČR GA522/01/0275 Grant - others:Volkswagen Stiftung(DE) I/76 865 Institutional research plan: CEZ:AV0Z5038910; CEZ:MSM 153100008 Keywords : Liquid chromatography mass spectrometry * Cytokinins Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 2.210, year: 2003

Influence of decreased level of endogenous cytokinins on antioxidative mechanisms in tobacco leaves during ageing

Czech Academy of Sciences Publication Activity Database

Mýtinová, Zuzana; Wilhelmová, Naděžda; Haisel, Daniel; Motyka, Václav

2005-01-01

Roč. 49, Supplement 1 (2005), S24-S24 ISSN 0006-3134 R&D Projects: GA ČR GA522/03/0312 Institutional research plan: CEZ:AV0Z50380511 Keywords : Cytokinins * senescence * Nicotiana tabacum L. Subject RIV: CE - Biochemistry Impact factor: 0.792, year: 2005

Cytokinin, auxin and physiological polarity in the aquatic carnivorous plants Aldrovanda vesiculosa and Utricularia australis

Czech Academy of Sciences Publication Activity Database

Šimura, Jan; Spíchal, Lukáš; Adamec, Lubomír; Pěnčík, A.; Rolčík, Jakub; Novák, Ondřej; Strnad, Miroslav

2016-01-01

Roč. 117, č. 6 (2016), s. 1037-1044 ISSN 0305-7364 R&D Projects: GA MŠk(CZ) LO1204; GA MŠk LK21306 Institutional support: RVO:61389030 ; RVO:67985939 Keywords : Auxin * Aldrovanda vesiculosa * cytokinin Subject RIV: EF - Botanics Impact factor: 4.041, year: 2016

A SWI/SNF Chromatin Remodelling Protein Controls Cytokinin Production through the Regulation of Chromatin Architecture

KAUST Repository

Jégu, Teddy

2015-10-12

Chromatin architecture determines transcriptional accessibility to DNA and consequently gene expression levels in response to developmental and environmental stimuli. Recently, chromatin remodelers such as SWI/SNF complexes have been recognized as key regulators of chromatin architecture. To gain insight into the function of these complexes during root development, we have analyzed Arabidopsis knock-down lines for one sub-unit of SWI/SNF complexes: BAF60. Here, we show that BAF60 is a positive regulator of root development and cell cycle progression in the root meristem via its ability to down-regulate cytokinin production. By opposing both the deposition of active histone marks and the formation of a chromatin regulatory loop, BAF60 negatively regulates two crucial target genes for cytokinin biosynthesis (IPT3 and IPT7) and one cell cycle inhibitor (KRP7). Our results demonstrate that SWI/SNF complexes containing BAF60 are key factors governing the equilibrium between formation and dissociation of a chromatin loop controlling phytohormone production and cell cycle progression.

A SWI/SNF Chromatin Remodelling Protein Controls Cytokinin Production through the Regulation of Chromatin Architecture

KAUST Repository

Jé gu, Teddy; Domenichini, Sé verine; Blein, Thomas; Ariel, Federico; Christ, Auré lie; Kim, SoonKap; Crespi, Martin; Boutet-Mercey, Sté phanie; Mouille, Gré gory; Bourge, Mickaë l; Hirt, Heribert; Bergounioux, Catherine; Raynaud, Cé cile; Benhamed, Moussa

2015-01-01

Chromatin architecture determines transcriptional accessibility to DNA and consequently gene expression levels in response to developmental and environmental stimuli. Recently, chromatin remodelers such as SWI/SNF complexes have been recognized as key regulators of chromatin architecture. To gain insight into the function of these complexes during root development, we have analyzed Arabidopsis knock-down lines for one sub-unit of SWI/SNF complexes: BAF60. Here, we show that BAF60 is a positive regulator of root development and cell cycle progression in the root meristem via its ability to down-regulate cytokinin production. By opposing both the deposition of active histone marks and the formation of a chromatin regulatory loop, BAF60 negatively regulates two crucial target genes for cytokinin biosynthesis (IPT3 and IPT7) and one cell cycle inhibitor (KRP7). Our results demonstrate that SWI/SNF complexes containing BAF60 are key factors governing the equilibrium between formation and dissociation of a chromatin loop controlling phytohormone production and cell cycle progression.

The natural cytokinin 2OH3MeOBAR induces cell death by a mechanism that is different from that of the „classical“ cytokinin ribosides

Czech Academy of Sciences Publication Activity Database

Voller, Jiří; Béres, T.; Zatloukal, M.; Kaminski, P. A.; Niemann, P.; Doležal, K.; Džubák, P.; Hajdúch, M.; Strnad, Miroslav

2017-01-01

Roč. 136, APR (2017), s. 156-164 ISSN 0031-9422 R&D Projects: GA MŠk(CZ) LO1204; GA MŠk(CZ) LO1304; GA MŠk(CZ) LM2015064; GA MŠk LM2015063; GA ČR GA14-19590S Institutional support: RVO:61389030 Keywords : myeloid-leukemia cells * kinetin-riboside * hl-60 cells * cancer-cells * in-vitro * apoptosis * gene * rcl * identification * lines * Phytohormone * Cytokinin * Leukemia * Cancer * Apoptosis * NCI60 panel Subject RIV: EB - Genetics ; Molecular Biology OBOR OECD: Plant sciences, botany Impact factor: 3.205, year: 2016

Degradation of quinoline by wet oxidation - kinetic aspects and reaction mechanisms

DEFF Research Database (Denmark)

Thomsen, A.B.

1998-01-01

The high temperature, high pressure wet oxidation reaction of quinoline has been studied as a function of initial concentration, pH and temperature. At neutral to acidic pH, it is effective in the oxidation of quinoline at 240 degrees C and above, whereas under alkaline conditions the reaction...... is markedly slowed down. The results indicate that the reaction is an auto-catalysed, free radical chain reaction transforming 99% of quinoline to other substances. Of the quinoline. 30-50% was oxidised to CO2 and H2O depending on the initial concentration. Wet oxidation of deuterium-labelled quinoline...

{8-14C}-Adenine and {1-14C}-isopentenyl pyrophosphate - precursors for root-produced cytokinins in the tomato (Lycopersicon esculentum mill.)

International Nuclear Information System (INIS)

Dickinson, J.R.

1985-01-01

Following the detection of reasonable levels of biologically active cytokinin-like compounds in one-month-old tomato plants, the possible involvement of {8- 14 C}-adenine and {1- 14 C}-isopentenyl pyrophosphate in the biosynthetic pathway leading to an accumulation of free zeatin derivatives, was studied. Intact tomato plants were used for a time-course study involving the uptake of {8- 14 C}-adenine and the tentative identification of compounds into which the 14 C became incorporated. Using high performance liquid chromatography, radioactive trans-zeatin was identified as being present in the Dowex 50 root extract. The 12-hour time interval was used and the roots of the tomato plants were immersed in a more heavily radiolabelled medium. Modified separation techniques were used to achieve enhanced radioactivity recovery rates. This experiment demonstrated the presence of relatively high levels of tentatively identified radioactive zeatin in the Dowex 50 root and stem extracts. Radioactivity in the aqueous extracts was found not to be contributed by cytokinin nucleotides. A final experiment was carried out using decapitated root systems to determine if the root tissue alone could be implicated in the synthesis of cytokinins. Decapitated tomato root systems were supplied with either {8- 14 C}-adenine or {1- 14 C}-isopentenyl pyrophosphate. The ratio of incorporation of {1- 14 C}-isopentenyl pyrophosphate into identified cytokinins was higher than for {8- 14 C}-adenine. It was concluded that both adenine and isopentenyl pyrophosphate are involved in the biosynthetic pathway leading to an accumulation of free zeatin derivatives in tomato roots

Genetic engineering of cytokinin metabolism: prospective way to improve agricultural traits of crop plants.

Science.gov (United States)

Zalabák, David; Pospíšilová, Hana; Šmehilová, Mária; Mrízová, Katarína; Frébort, Ivo; Galuszka, Petr

2013-01-01

Cytokinins (CKs) are ubiquitous phytohormones that participate in development, morphogenesis and many physiological processes throughout plant kingdom. In higher plants, mutants and transgenic cells and tissues with altered activity of CK metabolic enzymes or perception machinery, have highlighted their crucial involvement in different agriculturally important traits, such as productivity, increased tolerance to various stresses and overall plant morphology. Furthermore, recent precise metabolomic analyses have elucidated the specific occurrence and distinct functions of different CK types in various plant species. Thus, smooth manipulation of active CK levels in a spatial and temporal way could be a very potent tool for plant biotechnology in the future. This review summarises recent advances in cytokinin research ranging from transgenic alteration of CK biosynthetic, degradation and glucosylation activities and CK perception to detailed elucidation of molecular processes, in which CKs work as a trigger in model plants. The first attempts to improve the quality of crop plants, focused on cereals are discussed, together with proposed mechanism of action of the responses involved. Copyright © 2011 Elsevier Inc. All rights reserved.

Endogenous cytokinin and auxin profiles during in vitro organogenesis from vegetative buds of Pinus radiata adult trees

Czech Academy of Sciences Publication Activity Database

Montalban, I.A.; Novák, Ondřej; Rolčík, Jakub; Strnad, Miroslav; Moncalean, P.

2013-01-01

Roč. 148, č. 2 (2013), s. 214-231 ISSN 0031-9317 Institutional research plan: CEZ:AV0Z50380511 Keywords : ACTINIDIA-DELICIOSA * SHOOT ORGANOGENESIS * AROMATIC CYTOKININS Subject RIV: EF - Botanics Impact factor: 3.262, year: 2013

Modelling and simulation of a transketolase mediated reaction: Sensitivity analysis of kinetic parameters

DEFF Research Database (Denmark)

Sayar, N.A.; Chen, B.H.; Lye, G.J.

2009-01-01

In this paper we have used a proposed mathematical model, describing the carbon-carbon bond format ion reaction between beta-hydroxypyruvate and glycolaldehyde to synthesise L-erythrulose, catalysed by the enzyme transketolase, for the analysis of the sensitivity of the process to its kinetic...

Cytokinin levels and signaling respond to wounding and the perception of herbivore elicitors in Nicotiana attenuata

Czech Academy of Sciences Publication Activity Database

Schäfer, M.; Meza-Canales, I.D.; Navarro-Quezada, A.; Brütting, C.; Vaňková, Radomíra; Baldwin, I.T.; Meldau, S.

2015-01-01

Roč. 57, č. 2 (2015), s. 198-212 ISSN 1672-9072 R&D Projects: GA ČR GA206/09/2062 Institutional support: RVO:61389030 Keywords : Arabidopsis thaliana * cytokinin * herbivore-associated molecular patterns Subject RIV: ED - Physiology Impact factor: 3.670, year: 2015

Effects of light quality on apical dominance in Xanthium strumarium and the associated changes in endogenous levels of abscisic acid and cytokinins.

Science.gov (United States)

Tucker, D J; Mansfield, T A

1971-06-01

Apical dominance in Xanthium strumarium was influenced by the quality of illumination received at the end of the photoperiod. The involvement of the red/far-red regions of the spectrum was apparent. The persistence of the effects was partially dependent on the age of the individual buds concerned. Plants receiving 30 minutes of illumination from tungsten lamps after a 16-hour photoperiod from fluorescent tubes failed to branch, whereas plants given an identical photoperiod, both in terms of day-length and photosynthetically available light energy, but lacking the far-red from tungsten lamps, branched profusely.The influence of the spectral distribution of illumination on the levels of cytokinins and abseisic acid in the plant, and the correlation with the degree of branching, is presented and discussed. The cytokinin content was much higher in inhibited than released buds. The cytokinins present were probably not able to particinate in bud growth because of an accumulation of inhibitors resembling abscisic acid. The concentration of the inhibitors in inhibited buds was 50 to 250 times that occurring in all other plant parts examined.

A novel aromatic alcohol dehydrogenase in higher plants: molecular cloning and expression.

Science.gov (United States)

Goffner, D; Van Doorsselaere, J; Yahiaoui, N; Samaj, J; Grima-Pettenati, J; Boudet, A M

1998-03-01

Cinnamyl alcohol dehydrogenase (CAD; EC 1.1.195) catalyses the conversion of p-hydroxy-cinnamaldehydes to the corresponding alcohols and is considered a key enzyme in lignin biosynthesis. In a previous study, an atypical form of CAD (CAD 1) was identified in Eucalyptus gunnii [12]. We report here the molecular cloning and characterization of the corresponding cDNA, CAD 1-5, which encodes this novel aromatic alcohol dehydrogenase. The identity of CAD 1-5 was unambiguously confirmed by sequence comparison of the cDNA with peptide sequences derived from purified CAD 1 protein and by functional expression of CAD 1 recombinant protein in Escherichia coli. Both native and recombinant CAD 1 exhibit high affinity towards lignin precursors including 4-coumaraldehyde and coniferaldehyde, but they do not accept sinapaldehyde. Moreover, recombinant CAD 1 can also utilize a wide range of aromatic substrates including unsubstituted and substituted benzaldehydes. The open reading frame of CAD 1-5 encodes a protein with a calculated molecular mass of 35,790 Da and an isoelectric point of 8.1. Although sequence comparisons with proteins in databases revealed significant similarities with dihydroflavonol-4-reductases (DFR; EC 1.1.1.219) from a wide range of plant species, the most striking similarity was found with cinnamoyl-CoA reductase (CCR; EC 1.2.1.44), the enzyme which directly precedes CAD in the lignin biosynthetic pathway. RNA blot analysis and immunolocalization experiments indicated that CAD 1 is expressed in both lignified and unlignified tissues/cells. Based on the catalytic activity of CAD 1 in vitro and its localization in planta, CAD 1 may function as an 'alternative' enzyme in the lignin biosynthetic pathway. However, additional roles in phenolic metabolism are not excluded.

Heterogeneously Catalysed Aldol Reactions in Supercritical Carbon Dioxide as Innovative and Non-Flammable Reaction Medium

DEFF Research Database (Denmark)

Musko, Nikolai; Grunwaldt, Jan-Dierk

2011-01-01

Aldol reactions of several aldehydes have been investigated over acidic and basic catalysts in supercritical carbon dioxide at 180 bar and 100 °C. Both acidic (Amberlyst-15, tungstosilicic acid (TSA) on SiO2 and MCM-41) and basic (hydrotalcite) materials showed interesting performance in this pre...

Solvent-free lipase catalysed synthesis of diacylgycerols as low-calorie food ingredients

Directory of Open Access Journals (Sweden)

Luis eVazquez

2016-02-01

Full Text Available Problems derived from obesity and overweight have recently promoted the development of fat substitutes and other low-calorie foods. On the one hand, fats with short and medium chain fatty acids are a source of quick energy, easily hydrolyzable and hardly stored as fat. Furthermore, 1,3-diacylglycerols are not hydrolyzed to 2-monoacylglycerols in the gastrointestinal tract, reducing the formation of chylomicron and lowers the serum level of triacylglycerols by decreasing its re-synthesis in the enterocyte and its metabolism and absorption by the enterocyte are limited in comparison with the TAG, reducing chylomicron formation. In this work these two effects were combined to synthesize short and medium chain 1,3 diacylglycerols, leading to a product with great potential as for their low-calorie properties. Lipase catalysed transesterification reactions were performed between short and medium chain fatty acid ethyl esters and glycerol. Different variables were investigated such as the type of biocatalyst, the molar ratio FAEE:glycerol, the adsorption of glycerol on silica gel or the addition of lecithin. Best reaction conditions were evaluated considering the conversion intopercentage of 1,3-DAG produced and the reaction rate. Except Novozym 435 (Candida antarctica, other lipases required the adsorption of glycerol on silica gel to form acylglycerols. Lipases that gave the best results with adsorption were Novozym 435 and Lipozyme RM IM (Rhizomucor miehei with 52% and 60.7% of DAG at 32 h, respectively. Because of its specificity for sn-1 and sn-3 positions, lipases leading to a higher proportion of 1,3-DAG vs 1,2-DAG were Lipozyme RM IM (39.8% and 20.9%, respectively and Lipase PLG (Alcaligenes sp. (35.9% and 19.3%, respectively. By adding 1% (w/w of lecithin to the reaction with Novozym 435 and raw glycerol the reaction rate was considerably increased from 41.7% to 52.8% DAG at 24 h.

Response surface methodological approach for optimizing production of geranyl propionate catalysed by carbon nanotubes nanobioconjugates

International Nuclear Information System (INIS)

Mohamad, NurRoyhaila; Mahat, Naji Arafat; Wahab, Roswanira Abdul; Huyop, Fahrul; Aboul-Enein, Hassan Youssef

2015-01-01

Terpene esters of short-chain fatty acids are essential oils that have big importance in food, cosmetic and pharmaceutical industries as flavours and fragrances. Geraniol and citronellol are the most important substances. Considering the everincreasing demand for such products, their enzymatic production from natural raw materials by using environmentally friendly and economically attractive processes may prove advantageous. In this contribution, we would like to present an alternative option for the production of geranyl propionate using nanobioconjugates consisting of Candida rugosa lipase adsorbed onto multi-walled carbon nanotubes (CRL-MWCNTs). We investigated the effects of incubation time, temperature, solvent log P and substrate molar ratio, and determined the optimum conditions. The yield of geranyl propionate catalysed by CRL-MWCNTs nanobioconjugates was significantly influenced by two factors, namely, temperature and time of the reaction. Under the optimum reaction conditions of 55 C, solvent n-heptane (log P D 4.0), geraniol to propionic acid molar ratio of 5:1 and reaction time of 6 h, the use of CRL-MWCNTs resulted in 51.3% production of geranyl propionate. Therefore, the investigation revealed that geranyl propionate was successfully synthesized under mild conditions with reasonably high yield within a short period of time. The CRL-MWCNTs nanobioconjugates demonstrated a potential as economical and environmentally smarter biocatalysts for the production of geranyl propionate. Keywords: nanobioconjugates

Carbon dioxide/methanol conversion cycle based on cascade enzymatic reactions supported on superparamagnetic nanoparticles

Directory of Open Access Journals (Sweden)

CATERINA G.C. MARQUES NETTO

2017-10-01

Full Text Available ABSTRACT The conversion of carbon dioxide into important industrial feedstock is a subject of growing interest in modern society. A possible way to achieve this goal is by carrying out the CO2/methanol cascade reaction, allowing the recycle of CO2 using either chemical catalysts or enzymes. Efficient and selective reactions can be performed by enzymes; however, due to their low stability, immobilization protocols are required to improve their performance. The cascade reaction to reduce carbon dioxide into methanol has been explored by the authors, using, sequentially, alcohol dehydrogenase (ADH, formaldehyde dehydrogenase (FalDH, and formate dehydrogenase (FDH, powered by NAD+/NADH and glutamate dehydrogenase (GDH as the co-enzyme regenerating system. All the enzymes have been immobilized on functionalized magnetite nanoparticles, and their reactions investigated separately in order to establish the best performance conditions. Although the stepwise scheme led to only 2.3% yield of methanol per NADH; in a batch system under CO2 pressure, the combination of the four immobilized enzymes increased the methanol yield by 64 fold. The studies indicated a successful regeneration of NADH in situ, envisaging a real possibility of using immobilized enzymes to perform the cascade CO2-methanol reaction.

An improved in vivo deuterium labeling method for measuring the biosynthetic rate of cytokinins

Czech Academy of Sciences Publication Activity Database

Tarkowski, Petr; Floková, K.; Václavíková, Kateřina; Jaworek, P.; Raus, M.; Nordström, A.; Novák, Ondřej; Doležal, Karel; Šebela, M.; Frébortová, Jitka

2010-01-01

Roč. 15, č. 12 (2010), s. 9214-9229 ISSN 1420-3049 R&D Projects: GA ČR(CZ) GA522/08/0920; GA MŠk ED0017/01/01; GA ČR GA301/08/1649 Institutional research plan: CEZ:AV0Z50380511 Keywords : cytokinin * deuterium labelling * biosynthetic rate Subject RIV: CE - Biochemistry Impact factor: 1.988, year: 2010

Production of cytokinin-like substances and ethylene by the ectomycorrhizal fungus Cantharellus cibarius

Directory of Open Access Journals (Sweden)

Edmund Strzelczyk

2014-08-01

Full Text Available It was found that the hardwood form of Cantharellus cibarius (strain 5400 produced less cytokinin-like substances than the coniferous form (strain 5410. Among the active substances the following were detected: 2iP, 2iP riboside and zeatin. No significant differences in ethylene production between both strains in the presence or absence of methionine (considered to be the precursor of this gas were noted.

Positive selection on D-lactate dehydrogenases of Lactobacillus delbrueckii subspecies bulgaricus.

Science.gov (United States)

Zhang, Jifeng; Gong, Guangyu; Wang, Xiao; Zhang, Hao; Tian, Weidong

2015-08-01

Lactobacillus delbrueckii has been widely used for yogurt fermentation. It has genes encoding both D- and L-type lactate dehydrogenases (LDHs) that catalyse the production of L(+) or D(-) stereoisomer of lactic acid. D-lactic acid is the primary lactate product by L. delbrueckii, yet it cannot be metabolised by human intestine. Since it has been domesticated for long time, an interesting question arises regarding to whether the selection pressure has affected the evolution of both L-LDH and D-LDH genes in the genome. To answer this question, in this study the authors first investigated the evolution of these two genes by constructing phylogenetic trees. They found that D-LDH-based phylogenetic tree could better represent the phylogenetic relationship in the acidophilus complex than L-LDH-based tree. They next investigated the evolutions of LDH genes of L. delbrueckii at amino acid level, and found that D-LDH gene in L. delbrueckii is positively selected, possibly a consequence of long-term domestication. They further identified four amino acids that are under positive selection. One of them, V261, is located at the centre of three catalytic active sites, indicating likely functional effects on the enzyme activity. The selection from the domestication process thus provides direction for future engineering of D-LDH.

On the Mechanism of the Digold(I)-Hydroxide-Catalysed Hydrophenoxylation of Alkynes

KAUST Repository

Gó mez-Suá rez, Adriá n; Oonishi, Yoshihiro; Martin, Anthony R.; Vummaleti, Sai V. C.; Nelson, David J.; Cordes, David B.; Slawin, Alexandra M. Z.; Cavallo, Luigi; Nolan, Steven P.; Poater, Albert

2015-01-01

Herein, we present a detailed investigation of the mechanistic aspects of the dual gold-catalysed hydrophenoxylation of alkynes by both experimental and computational methods. The dissociation of [{Au(NHC)}2(μ-OH)][BF4] is essential to enter

The role of auxin and cytokinin signalling in specifying the root architecture of Arabidopsis thaliana

KAUST Repository

Muraro, Daniele

2013-01-01

Auxin and cytokinin are key hormonal signals that control the cellular architecture of the primary root and the initiation of new lateral root organs in the plant Arabidopsis thaliana. Both developmental processes are regulated by cross-talk between these hormones and their signalling pathways. In this paper, sub-cellular and multi-cellular mathematical models are developed to investigate how interactions between auxin and cytokinin influence the size and location of regions of division and differentiation within the primary root, and describe how their cross-regulation may cause periodic branching of lateral roots. We show how their joint activity may influence tissue-specific oscillations in gene expression, as shown in Moreno-Risueno et al. (2010) and commented upon in Traas and Vernoux (2010), and we propose mechanisms that may generate synchronisation of such periodic behaviours inside a cell and with its neighbours. Using a multi-cellular model, we also analyse the roles of cytokinin and auxin in specifying the three main regions of the primary root (elongation, transition and division zones), our simulation results being in good agreement with independent experimental observations. We then use our model to generate testable predictions concerning the effect of varying the concentrations of the auxin efflux transporters on the sizes of the different root regions. In particular, we predict that over-expression of the transporters will generate a longer root with a longer elongation zone and a smaller division zone than that of a wild type root. This root will contain fewer cells than its wild type counterpart. We conclude that our model can provide a useful tool for investigating the response of cell division and elongation to perturbations in hormonal signalling. © 2012 Elsevier Ltd.

Rhodococcus fascians Impacts Plant Development Through the Dynamic Fas-Mediated Production of a Cytokinin Mix

Czech Academy of Sciences Publication Activity Database

Pertry, I.; Václavíková, Kateřina; Gemrotová, Markéta; Spíchal, Lukáš; Galuszka, Petr; Depuydt, S.; Temmerman, W.; Stes, E.; De Keyser, A.; Riefler, M.; Biondi, S.; Novák, Ondřej; Schmülling, T.; Strnad, Miroslav; Tarkowski, Petr; Holsters, M.; Vereecke, D.

2010-01-01

Roč. 23, č. 9 (2010), s. 1164-1174 ISSN 0894-0282 R&D Projects: GA MŠk(CZ) LC06034; GA ČR GD522/08/H003 Institutional research plan: CEZ:AV0Z50380511 Keywords : LEAFY GALL FORMATION * CORYNEBACTERIUM-FASCIANS * ENDOGENOUS CYTOKININS Subject RIV: ED - Physiology Impact factor: 4.010, year: 2010

Multiple alcohol dehydrogenases but no functional acetaldehyde dehydrogenase causing excessive acetaldehyde production from ethanol by oral streptococci.

Science.gov (United States)

Pavlova, Sylvia I; Jin, Ling; Gasparovich, Stephen R; Tao, Lin

2013-07-01

Ethanol consumption and poor oral hygiene are risk factors for oral and oesophageal cancers. Although oral streptococci have been found to produce excessive acetaldehyde from ethanol, little is known about the mechanism by which this carcinogen is produced. By screening 52 strains of diverse oral streptococcal species, we identified Streptococcus gordonii V2016 that produced the most acetaldehyde from ethanol. We then constructed gene deletion mutants in this strain and analysed them for alcohol and acetaldehyde dehydrogenases by zymograms. The results showed that S. gordonii V2016 expressed three primary alcohol dehydrogenases, AdhA, AdhB and AdhE, which all oxidize ethanol to acetaldehyde, but their preferred substrates were 1-propanol, 1-butanol and ethanol, respectively. Two additional dehydrogenases, S-AdhA and TdhA, were identified with specificities to the secondary alcohol 2-propanol and threonine, respectively, but not to ethanol. S. gordonii V2016 did not show a detectable acetaldehyde dehydrogenase even though its adhE gene encodes a putative bifunctional acetaldehyde/alcohol dehydrogenase. Mutants with adhE deletion showed greater tolerance to ethanol in comparison with the wild-type and mutant with adhA or adhB deletion, indicating that AdhE is the major alcohol dehydrogenase in S. gordonii. Analysis of 19 additional strains of S. gordonii, S. mitis, S. oralis, S. salivarius and S. sanguinis showed expressions of up to three alcohol dehydrogenases, but none showed detectable acetaldehyde dehydrogenase, except one strain that showed a novel ALDH. Therefore, expression of multiple alcohol dehydrogenases but no functional acetaldehyde dehydrogenase may contribute to excessive production of acetaldehyde from ethanol by certain oral streptococci.

Glycolysis of carbon fiber-epoxy unidirectional mat catalysed by sodium hydroxide

Science.gov (United States)

Zaini, Mariana Binti Mohd; Badri, Khairiah Haji

2014-09-01

This study was conducted to recycle carbon fibre-epoxy (CFRP) composite in woven sheet/ mat form. The CFRP was recycled through glycolysis with polyethlyene glycol (PEG 200) as the solvent. The CFRP was loaded into the solvent at a ratio of 4:1 (w/w). PEG200 was diluted with water to a ratio of 80:20 (v/v). This reaction was catalysed by sodium hydroxide (NaOH) solution with varying concentrations at 1.5, 1.7 and 1.9% (w/v). The glycolysis was conducted at 180-190 °C. The recovered CF (rCF) was analysed using Fourier Transform Infrared (FTIR), Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray (EDX) while the degraded solution was analysed using FTIR and the epoxy content was determined. The FTIR spectrum of the rCF exhibited the disappearance of the COC peak belonged to epoxy and supported by the SEM micrographs that showed clear rCF. On the other hand, the analysed filtrate detected the disappearance of oxygen peak element in the EDX spectrum for all rCF samples. This gave an indication that the epoxy resin has been removed from the surface of the carbon fiber.

Glycolysis of carbon fiber-epoxy unidirectional mat catalysed by sodium hydroxide

Energy Technology Data Exchange (ETDEWEB)

Zaini, Mariana Binti Mohd [School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor (Malaysia); Badri, Khairiah Haji [School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor, Malaysia and Polymer Research Center, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43 (Malaysia)

2014-09-03

This study was conducted to recycle carbon fibre-epoxy (CFRP) composite in woven sheet/ mat form. The CFRP was recycled through glycolysis with polyethlyene glycol (PEG 200) as the solvent. The CFRP was loaded into the solvent at a ratio of 4:1 (w/w). PEG200 was diluted with water to a ratio of 80:20 (v/v). This reaction was catalysed by sodium hydroxide (NaOH) solution with varying concentrations at 1.5, 1.7 and 1.9% (w/v). The glycolysis was conducted at 180-190 °C. The recovered CF (rCF) was analysed using Fourier Transform Infrared (FTIR), Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray (EDX) while the degraded solution was analysed using FTIR and the epoxy content was determined. The FTIR spectrum of the rCF exhibited the disappearance of the COC peak belonged to epoxy and supported by the SEM micrographs that showed clear rCF. On the other hand, the analysed filtrate detected the disappearance of oxygen peak element in the EDX spectrum for all rCF samples. This gave an indication that the epoxy resin has been removed from the surface of the carbon fiber.

Modulations of RNA sequences by cytokinin in pumpkin cotyledons

International Nuclear Information System (INIS)

Chang, C.; Ertl, J.; Chen, C.

1987-01-01

Polyadenylated mRNAs from excised pumpkin cotyledons treated with or without 10 -4 M benzyladenine (BA) for various time periods in suspension culture were assayed by in vitro translation in the presence of [ 35 S] methionine. The radioactive polypeptides were analyzed by one- and two-dimensional polyacrylamide gel electrophoresis. Specific sequences of mRNAs were enhanced, reduced, induced, or suppressed by the hormone within 60 min of the application of BA to the cotyledons. Four independent cDNA clones of cytokinin-modulated mRNAs have been selected and characterized. RNA blot hybridization using the four cDNA probes also indicates that the levels of specific mRNAs are modulated upward or downward by the hormone

Circadian Stress Regimes Affect the Circadian Clock and Cause Jasmonic Acid-Dependent Cell Death in Cytokinin-Deficient Arabidopsis Plants[OPEN

Science.gov (United States)

Nitschke, Silvia; Cortleven, Anne; Iven, Tim; Havaux, Michel; Schmülling, Thomas

2016-01-01

The circadian clock helps plants measure daylength and adapt to changes in the day-night rhythm. We found that changes in the light-dark regime triggered stress responses, eventually leading to cell death, in leaves of Arabidopsis thaliana plants with reduced cytokinin levels or defective cytokinin signaling. Prolonged light treatment followed by a dark period induced stress and cell death marker genes while reducing photosynthetic efficiency. This response, called circadian stress, is also characterized by altered expression of clock and clock output genes. In particular, this treatment strongly reduced the expression of CIRCADIAN CLOCK ASSOCIATED1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY). Intriguingly, similar changes in gene expression and cell death were observed in clock mutants lacking proper CCA1 and LHY function. Circadian stress caused strong changes in reactive oxygen species- and jasmonic acid (JA)-related gene expression. The activation of the JA pathway, involving the accumulation of JA metabolites, was crucial for the induction of cell death, since the cell death phenotype was strongly reduced in the jasmonate resistant1 mutant background. We propose that adaptation to circadian stress regimes requires a normal cytokinin status which, acting primarily through the AHK3 receptor, supports circadian clock function to guard against the detrimental effects of circadian stress. PMID:27354555

STIMULATION PAR LES CYTOKININES DE L’ACCUMULATION ALCALOÏDIQUE DANS DES SUSPENSIONS CELLULAIRES: IMPLICATION DE L’ETHYLENE COMME SECOND MESSAGER ?

Directory of Open Access Journals (Sweden)

A YAHIA

1999-12-01

Full Text Available Dans ce travail, nous avons cherché à savoir si l’éthylène pouvait être impliquée lors de la stimulation de la production alcaloïdique par les cytokinines dans les suspensions cellulaires de Catharanthus roseus. La stratégie expérimentale a été double: 1 modifier les teneurs en éthylène endogène en traitant les cellules par différents agonistes ou antagonistes de la voie de biosynthèse de l’éthylène, 2 soumettre les cellules à des apports exogène d’éthylène.      Les résultats obtenus montrent que les inhibiteurs de l’éthylène AVG, Co+2  bloquent partiellement la stimulation alcaloïdique dans les cellules traitées par les cytokinines alors que le précurseur de l’éthylène ACC n’a pas d’effet sur la production alcaloïdique dans les cellules non traitées par les cytokinines. En revanche, lorsque l’éthylène est apporté de manière exogène (traitement par l’éthephon, la production alcaloïdique est multipliée par quatre.

A parasitic nematode releases cytokinin that controls cell division and orchestrates feeding site formation in host plants

Czech Academy of Sciences Publication Activity Database

Siddique, S.; Radakovic, Z.S.; De La Torre, C.M.; Chronis, D.; Novák, Ondřej; Ramireddy, E.; Holbein, J.; Matera, C.; Hutten, M.; Gutbrod, P.; Anjam, M.S.; Rozanska, E.; Habash, S.; Elashry, A.; Sobczak, M.; Kakimoto, T.; Strnad, Miroslav; Schmülling, T.; Mitchum, M.G.; Grundler, F.M.W.

2015-01-01

Roč. 112, č. 41 (2015), s. 12669-12674 ISSN 0027-8424 R&D Projects: GA MŠk(CZ) LO1204 Institutional support: RVO:61389030 Keywords : Arabidopsis thaliana * cell cycle * cytokinin Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 9.423, year: 2015

Endogenous cytokinin dynamics in micropropagated tulips during bulb formation process influenced by TDZ and iP pretreatment

Czech Academy of Sciences Publication Activity Database

Podwyszynska, M.; Novák, Ondřej; Doležal, Karel; Strnad, Miroslav

2014-01-01

Roč. 119, č. 2 (2014), s. 331-346 ISSN 0167-6857 R&D Projects: GA MŠk(CZ) LO1204 Institutional support: RVO:61389030 Keywords : Tulipa gesneriana * Endogenous cytokinins * Micropropagation Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 2.125, year: 2014

Study of Cytokinin and Auxin Hormones and Planting Pattern Effects on Yield and Yield Components of Grain Maize (Zea mays L. under Saline Conditions

Directory of Open Access Journals (Sweden)

D Davani

2016-07-01

Full Text Available Introduction Maize (Zea mays L. which belongs to the Poaceae family is the third important cereal crop of the world after wheat and rice. Salinity is one of the major environmental factors limiting plant growth and productivity. Maize is sensitive to salinity. Planting method is a crucial factor for improving crop yield. Planting methods in saline and non-saline conditions are different. Kinetin is one of the cytokinins known to significantly improve the growth of crop plants grown under salinity. Indole acetic acid (IAA is also known to play a significant role in plant tolerance to salt stress. However, little information appears to be available on the relationship between salinity tolerance and auxin or cytokinins levels in plants. In this respect, the objective of this study was to study the effects of foliar applications of cytokinin and auxin hormones on yield and yield components of grain maize under different planting patterns in saline conditions. Materials and Methods The experiment was carried out at Bushehr Agricultural and Natural Resources Research Center, Dashtestan station with 29° 16´ E latitude and 51° 31´ N, longitude and 70 m above the see surface during the 2013 growing season. Dashtestan region is a warm-arid region with 250 mm precipitation per year. The field plowed by April 2013 and then prepared and sowed by August 2013. There were five rows with 75 cm distance. The experiment was conducted as a split-plot factorial design based on complete randomized blocks with three replications. Planting pattern (ridge planting, double rows of planting on a ridge in zigzag form and furrow planting as the main factor and time of cytokinin (0 as a control, V5- V6 stage and V8- V10 stage and auxin (0 as a control, silking stage, two weeks after silking stage foliar-applied was considered in a factorial. Cytokinin (Benzyl Adenine, Merck and Auxin (Indole-3-Butiric Acid, Merck were sprayed on the entire plant in the evening with

Cytokinins in Symbiotic Nodulation: When, Where, What For?

Science.gov (United States)

Gamas, Pascal; Brault, Mathias; Jardinaud, Marie-Françoise; Frugier, Florian

2017-09-01

Substantial progress has been made in the understanding of early stages of the symbiotic interaction between legume plants and rhizobium bacteria. Those include the specific recognition of symbiotic partners, the initiation of bacterial infection in root hair cells, and the inception of a specific organ in the root cortex, the nodule. Increasingly complex regulatory networks have been uncovered in which cytokinin (CK) phytohormones play essential roles in different aspects of early symbiotic stages. Intriguingly, these roles can be either positive or negative, cell autonomous or non-cell autonomous, and vary, depending on time, root tissues, and possibly legume species. Recent developments on CK symbiotic functions and interconnections with other signaling pathways during nodule initiation are the focus of this review. Copyright © 2017 Elsevier Ltd. All rights reserved.

The combination effect of auxin and cytokinin on in vitro callus formation of Physalis angulata L. - A medicinal plant

Science.gov (United States)

Mastuti, Retno; Munawarti, Aminatun; Firdiana, Elok Rifqi

2017-11-01

Physalis angulata L. (Ciplukan) is one member of Solanaceae that has a potential as herbal medicine. This plant grows wild in the crop fields, forest edges, etc. However, ciplukan is increasingly difficult to find recently. In vitro callus is an alternative source to produce secondary metabolite production as well as to regenerate plants through indirect organogenesis. This study aims to identify the response of hypocotyl explants on in vitro callus formation induced by a combination of auxin and cytokinins. Two types of cytokinins, Kinetin and BAP (0.5 ppm) were combined with three types of auxin, i.e. 2.4-D, IBA and IAA, at three concentrations 0.5, 1.0 and 1.5 ppm. In all combinations of cytokinin and auxin, 50-100% of hypocotyl explants derived from in vitro seedling were able to produce callus either in a compact or watery friable texture. In MS medium supplemented with 2.4-D, callus FW (fresh weight) began to decline in the fourth week after culture. Callus FW that increased until 5 weeks of culture was obtained in medium IAA 0.5 + Kin 0.5, IBA 1.0 + Kin 0.5 and IBA 1 + BA 0.5. Almost all calli induced on a medium + Kinetin also produced roots. While medium + BAP was able to induce shoots regeneration.

Biochemical characterization of ethanol-dependent reduction of furfural by alcohol dehydrogenases.

Science.gov (United States)

Li, Qunrui; Metthew Lam, L K; Xun, Luying

2011-11-01

Lignocellulosic biomass is usually converted to hydrolysates, which consist of sugars and sugar derivatives, such as furfural. Before yeast ferments sugars to ethanol, it reduces toxic furfural to non-inhibitory furfuryl alcohol in a prolonged lag phase. Bioreduction of furfural may shorten the lag phase. Cupriavidus necator JMP134 rapidly reduces furfural with a Zn-dependent alcohol dehydrogenase (FurX) at the expense of ethanol (Li et al. 2011). The mechanism of the ethanol-dependent reduction of furfural by FurX and three homologous alcohol dehydrogenases was investigated. The reduction consisted of two individual reactions: ethanol-dependent reduction of NAD(+) to NADH and then NADH-dependent reduction of furfural to furfuryl alcohol. The kinetic parameters of the coupled reaction and the individual reactions were determined for the four enzymes. The data indicated that limited NADH was released in the coupled reaction. The enzymes had high affinities for NADH (e.g., K ( d ) of 0.043 μM for the FurX-NADH complex) and relatively low affinities for NAD(+) (e.g., K ( d ) of 87 μM for FurX-NAD(+)). The kinetic data suggest that the four enzymes are efficient "furfural reductases" with either ethanol or NADH as the reducing power. The standard free energy change (ΔG°') for ethanol-dependent reduction of furfural was determined to be -1.1 kJ mol(-1). The physiological benefit for ethanol-dependent reduction of furfural is likely to replace toxic and recalcitrant furfural with less toxic and more biodegradable acetaldehyde.

Inhibition effects of furfural on alcohol dehydrogenase, aldehyde dehydrogenase and pyruvate dehydrogenase.

Science.gov (United States)

Modig, Tobias; Lidén, Gunnar; Taherzadeh, Mohammad J

2002-01-01

The kinetics of furfural inhibition of the enzymes alcohol dehydrogenase (ADH; EC 1.1.1.1), aldehyde dehydrogenase (AlDH; EC 1.2.1.5) and the pyruvate dehydrogenase (PDH) complex were studied in vitro. At a concentration of less than 2 mM furfural was found to decrease the activity of both PDH and AlDH by more than 90%, whereas the ADH activity decreased by less than 20% at the same concentration. Furfural inhibition of ADH and AlDH activities could be described well by a competitive inhibition model, whereas the inhibition of PDH was best described as non-competitive. The estimated K(m) value of AlDH for furfural was found to be about 5 microM, which was lower than that for acetaldehyde (10 microM). For ADH, however, the estimated K(m) value for furfural (1.2 mM) was higher than that for acetaldehyde (0.4 mM). The inhibition of the three enzymes by 5-hydroxymethylfurfural (HMF) was also measured. The inhibition caused by HMF of ADH was very similar to that caused by furfural. However, HMF did not inhibit either AlDH or PDH as severely as furfural. The inhibition effects on the three enzymes could well explain previously reported in vivo effects caused by furfural and HMF on the overall metabolism of Saccharomyces cerevisiae, suggesting a critical role of these enzymes in the observed inhibition. PMID:11964178

Abscisic Acid and Cytokinin-Induced Osmotic and Antioxidant Regulation in Two Drought-Tolerant and Drought-Sensitive Cultivars of Wheat During Grain Filling Under Water Deficit in Field Conditions

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Mohammad-Reza SARAFRAZ-ARDAKANI

2014-09-01

Full Text Available Phytohormones play critical roles in regulating plant responses to stress. The present study investigates the effect of cytokinin, abscisic acid and cytokinin/abscisic acid interaction on some osmoprotectants and antioxidant parameters induced by drought stress in two wheat cultivars (Triticum aestivum L. of ‘Pishgam’ and ‘MV-17’ as tolerant and sensitive to drought during post-anthesis phase, respectively grown in field conditions. The most considerable effect of the treatments was exhibited 21 days after anthesis. Under drought conditions, the flag leaf soluble carbohydrate content increased in both cultivars while starch content was remarkably decreased in ‘Pishgam’ as compared to ‘MV-17’. Abscisic acid increased total soluble sugar and reduced starch more than other hormonal treatments, although it decreased studied monosaccharaides in ‘Pishgam’, especially. Drought stress induced high proportion of gylycinebetain and free proline in ‘Pishgam’ cultivar. Application of abscisic acid and cytokinin/abscisic acid interaction increased gylycinebetain and proline content in both cultivars under irrigation and drought conditions. The tolerant cultivar exhibited less accumulation of hydrogen peroxide and malondialdehyde in relation to significant increase of catalase and peroxidase activities and α-tocpherol content under drought conditions. All hormonal treatments increased the named enzyme activities under both irrigation and drought conditions, while higher accumulation of α-tocopherol was only showed in case of cytokinin application. Also, abscisic acid and cytokinin/abscisic acid could decrease drought-induced hydrogen peroxide and malondialdehyde level to some extent, although abscisic acid increased both of hydrogen peroxide andmalondialdehyde content in irrigation phase, especially.

Over-expression of SOB5 suggests the involvement of a novel plant protein in cytokinin-mediated development

Czech Academy of Sciences Publication Activity Database

Zhang, J.; Wrage, E.L.; Vaňková, Radomíra; Malbeck, Jiří; Neff, M. M.

2006-01-01

Roč. 46, č. 5 (2006), s. 834-848 ISSN 0960-7412 R&D Projects: GA ČR GA522/04/0549 Institutional research plan: CEZ:AV0Z50380511 Keywords : SOB5 * SOFL * cytokinin Subject RIV: ED - Physiology Impact factor: 6.565, year: 2006

Polyphenol oxidases in Physcomitrella: functional PPO1 knockout modulates cytokinin-dependent developmentin the moss Physcomitrella patens

Czech Academy of Sciences Publication Activity Database

Richter, H.; Lieberei, R.; Strnad, Miroslav; Novák, Ondřej; Grúz, Jiří; Rensing, S. A.; von Schwartzenberg, K.

2012-01-01

Roč. 63, č. 14 (2012), s. 5121-5135 ISSN 0022-0957 Grant - others:GA MŠk(CZ) ED0007/01/01 Program:ED Institutional research plan: CEZ:AV0Z50380511 Keywords : Cytokinins * gene family * gene replacement Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 5.242, year: 2012

Base catalysed isomerisation of aldoses of the arabino and lyxo series in the presence of aluminate.

Science.gov (United States)

Ekeberg, Dag; Morgenlie, Svein; Stenstrøm, Yngve

2002-04-30

Base-catalysed isomerisation of aldoses of the arabino and lyxo series in aluminate solution has been investigated. L-Arabinose and D-galactose give L-erythro-2-pentulose (L-ribulose) and D-lyxo-2-hexulose (D-tagatose), respectively, in good yields, whereas lower reactivity is observed for 6-deoxy-D-galactose (D-fucose). From D-lyxose, D-mannose and 6-deoxy-L-mannose (L-rhamnose) are obtained mixtures of ketoses and C-2 epimeric aldoses. Small amounts of the 3-epimers of the ketoses were also formed. 6-Deoxy-L-arabino-2-hexulose (6-deoxy-L-fructose) and 6-deoxy-L-glucose (L-quinovose) were formed in low yields from 6-deoxy-L-mannose and isolated as their O-isopropylidene derivatives. Explanations of the differences in reactivity and course of the reaction have been suggested on the basis of steric effects.

Francis Farley presenting his novel "Catalysed Fusion" in the CERN Library

CERN Multimedia

Farley, Irina

2013-01-01

"Catalysed Fusion" is described by its author Francis Farley, 92, as a "true-to-life fantasy woven around particle physics" set in 1980s Geneva – "the city where nations meet and particles collide". Farley presented the book in the program "Literature in Focus" on Tuesday 16th April 2013.

Effects of lead nitrate on the activity of metabolic enzymes during early developmental stages of the African catfish, Clarias gariepinus (Burchell, 1822)

NARCIS (Netherlands)

Osman, A.G.M.; Mekkawy, Imam A.; Verreth, J.A.J.; Kirschbaum, Frank

2007-01-01

Glucose-6-phosphate dehydrogenase (G6PDH), lactate dehydrogenase (LDH) and pyruvate kinase (PK) are key metabolic enzymes. G6PDH has been used as a biomarker of pollution-induced carcinogenesis in fish. LDH has been used as marker of lesions in toxicology and clinical chemistry, and PK catalyses the

Structural organization of the human short-chain acyl-CoA dehydrogenase gene

DEFF Research Database (Denmark)

Corydon, M J; Andresen, B S; Bross, P

1997-01-01

Short-chain acyl-CoA dehydrogenase (SCAD) is a homotetrameric mitochondrial flavoenzyme that catalyzes the initial reaction in short-chain fatty acid beta-oxidation. Defects in the SCAD enzyme are associated with failure to thrive, often with neuromuscular dysfunction and elevated urinary excretion...... shown to be associated with ethylmalonic aciduria. From analysis of 18 unrelated Danish families, we show that the four SCAD gene polymorphisms constitute five allelic variants of the SCAD gene, and that the 625A variant together with the less frequent variant form of the three other polymorphisms (321C....... The evolutionary relationship between SCAD and five other members of the acyl-CoA dehydrogenase family was investigated by two independent approaches that gave similar phylogenetic trees....

Exploring the atmospheric chemistry of O2SO3- and assessing the maximum turnover number of ion-catalysed H2SO4 formation

DEFF Research Database (Denmark)

Bork, Nicolai Christian; Kurtén, T.; Vehkamäki, H.

2013-01-01

molecule, but reaction (b) is in general much more probable. Although we are unable to assess the overall importance of this cycle in the real atmosphere due to the unknown influence of CO2 and NOx, we roughly estimate that ion-induced catalysis may contribute with several percent of H2SO4 levels......It has recently been demonstrated that the O2SO3- ion forms in the atmosphere as a natural consequence of ionizing radiation. Here, we present a density functional theory-based study of the reactions of O2SO3- with O-3. The most important reactions are (a) oxidation to O3SO3- and (b) cluster...... the two major sinks for O2SO3- is assessed, thereby providing a measure of the maximum turnover number of ion-catalysed SO2 oxidation, i.e. how many SO2 can be oxidized per free electron. The rate ratio between reactions (a) and (b) is significantly altered by the presence or absence of a single water...

[Enzymatic conversion of tetradecanol in heterogenous phase by yeast-alcohol dehydrogenase].

Science.gov (United States)

Rothe, U; Schöpp, W; Aurich, H

1976-01-01

Alcohol dehydrogenase from yeast converts long-chain primary alcohols not only in the dissolved state, but also at the surface of undissolved particles. Tetradecanol beads with a defined surface can be produced and employed as model substrate. The reaction rate was determined by the proton release accomplished in the reaction. The initial reaction rate depends on the enzyme concentration. The relation is nonlinear (vi = k-[e]0,4); the numerical value of the exponent (n = 0.4) argues in favour of a reaction occurring at the interface. The Lineweaver-Burk plots become linear if the substrate concentrations are based on the molar surface concentrations of the particles. The pH optimum for the reaction at the surface is displaced by 0.25 pH units towards the alkaline region (compared with ethanol as substrate). The activation energy of the reaction with tetradecanol beads as substrate is 30% lower than that for the ethanol oxydation.

Redox-flexible NADH oxidase biosensor: A platform for various dehydrogenase bioassays and biosensors

International Nuclear Information System (INIS)

Serban, Simona; El Murr, Nabil

2006-01-01

A generic amperometric bioassay based on the enzymatic oxidation catalysed by the stable NADH oxidase (NAox) from Thermus thermophilus has been developed for NADH measurements. The NAox uses O 2 as its natural electron acceptor and produces H 2 O 2 in a two-electron process. Electrochemical and spectrophotometric experiments showed that the NAox used in this work, presents a very good activity towards its substrate and, in contrary to previously mentioned NADH oxidases, does not require the addition of any exogenous flavin cofactor neither to promote nor to maintain its activity. In addition, the NAox used also works with artificial electron acceptors like ferrocene derivatives. O 2 was successfully replaced by redox mediators such as hydroxymethyl ferrocene (FcCH 2 OH) for the regeneration of the active enzyme. Combining the NAox with the mediator and the horseradish peroxidase we developed an original, high sensitive 'redox-flexible' NADH amperometric bioassay working in a large window of applied potentials in both oxidation and reduction modes. The biosensor has a continuous and complementary linearity range permitting to measure NADH concentrations starting from 5 x 10 -6 M in reduction until 2 x 10 3 M in oxidation. This redox-flexibility allows choosing the applied potential in order to avoid electrochemical interferences. The association of the 'redox-flexible' concept with NADH dependent enzymes opens a novel strategy for dehydrogenases based bioassays and biosensors. The great number of dehydrogenases available makes the concept applicable for numerous substrates to analyse. Moreover it allows the development of a wide range of biosensors on the basis of a generic platform. This gives several advantages over the previous manufacturing techniques and offers a general and flexible scheme for the fabrication of biosensors presenting high sensitivities, wide calibration ranges and less affected by electrochemical interferences

Modelling Chemical Reasoning to Predict and Invent Reactions.

Science.gov (United States)

Segler, Marwin H S; Waller, Mark P

2017-05-02

The ability to reason beyond established knowledge allows organic chemists to solve synthetic problems and invent novel transformations. Herein, we propose a model that mimics chemical reasoning, and formalises reaction prediction as finding missing links in a knowledge graph. We have constructed a knowledge graph containing 14.4 million molecules and 8.2 million binary reactions, which represents the bulk of all chemical reactions ever published in the scientific literature. Our model outperforms a rule-based expert system in the reaction prediction task for 180 000 randomly selected binary reactions. The data-driven model generalises even beyond known reaction types, and is thus capable of effectively (re-)discovering novel transformations (even including transition metal-catalysed reactions). Our model enables computers to infer hypotheses about reactivity and reactions by only considering the intrinsic local structure of the graph and because each single reaction prediction is typically achieved in a sub-second time frame, the model can be used as a high-throughput generator of reaction hypotheses for reaction discovery. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The Pseudomonas type III effector HopQ1 activates cytokinin signaling and interferes with plant innate immunity

Czech Academy of Sciences Publication Activity Database

Hann, D.R.; Dominguez-Ferreras, A.; Motyka, Václav; Dobrev, Petre; Schornack, S.; Jehle, A.; Felix, G.; Chinchilla, D.; Rathjen, J.P.; Boller, T.

2014-01-01

Roč. 201, č. 2 (2014), s. 585-598 ISSN 1469-8137 R&D Projects: GA ČR GA13-26798S Institutional support: RVO:61389030 Keywords : cytokinin * flagellin * FLS2 Subject RIV: GF - Plant Pathology, Vermin, Weed, Plant Protection Impact factor: 6.545, year: 2013

Interaction of benzoate pyrimidine analogues with class 1A dihydroorotate dehydrogenase from Lactococcus lactis

DEFF Research Database (Denmark)

Wolfe, Abigail E; Thymark, Majbritt; Gattis, Samuel G

2007-01-01

Dihydroorotate dehydrogenases (DHODs) catalyze the oxidation of dihydroorotate to orotate in the only redox reaction in pyrimidine biosynthesis. The pyrimidine binding sites are very similar in all structurally characterized DHODs, suggesting that the prospects for identifying a class-specific in......-system of the flavin, resulting in a green color....

Evaluation of alcohol dehydrogenase and aldehyde dehydrogenase enzymes as bi-enzymatic anodes in a membraneless ethanol microfluidic fuel cell

Science.gov (United States)

Galindo-de-la-Rosa, J.; Arjona, N.; Arriaga, L. G.; Ledesma-García, J.; Guerra-Balcázar, M.

2015-12-01

Alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (AldH) enzymes were immobilized by covalent binding and used as the anode in a bi-enzymatic membraneless ethanol hybrid microfluidic fuel cell. The purpose of using both enzymes was to optimize the ethanol electro-oxidation reaction (EOR) by using ADH toward its direct oxidation and AldH for the oxidation of aldehydes as by-products of the EOR. For this reason, three enzymatic bioanode configurations were evaluated according with the location of enzymes: combined, vertical and horizontally separated. In the combined configuration, a current density of 16.3 mA cm-2, a voltage of 1.14 V and a power density of 7.02 mW cm-2 were obtained. When enzymes were separately placed in a horizontal and vertical position the ocp drops to 0.94 V and to 0.68 V, respectively. The current density also falls to values of 13.63 and 5.05 mA cm-2. The decrease of cell performance of bioanodes with separated enzymes compared with the combined bioanode was of 31.7% and 86.87% for the horizontal and the vertical array.

Palladium- and copper-mediated N-aryl bond formation reactions for the synthesis of biological active compounds

Directory of Open Access Journals (Sweden)

Burkhard Koenig

2011-01-01

Full Text Available N-Arylated aliphatic and aromatic amines are important substituents in many biologically active compounds. In the last few years, transition-metal-mediated N-aryl bond formation has become a standard procedure for the introduction of amines into aromatic systems. While N-arylation of simple aromatic halides by simple amines works with many of the described methods in high yield, the reactions may require detailed optimization if applied to the synthesis of complex molecules with additional functional groups, such as natural products or drugs. We discuss and compare in this review the three main N-arylation methods in their application to the synthesis of biologically active compounds: Palladium-catalysed Buchwald–Hartwig-type reactions, copper-mediated Ullmann-type and Chan–Lam-type N-arylation reactions. The discussed examples show that palladium-catalysed reactions are favoured for large-scale applications and tolerate sterically demanding substituents on the coupling partners better than Chan–Lam reactions. Chan–Lam N-arylations are particularly mild and do not require additional ligands, which facilitates the work-up. However, reaction times can be very long. Ullmann- and Buchwald–Hartwig-type methods have been used in intramolecular reactions, giving access to complex ring structures. All three N-arylation methods have specific advantages and disadvantages that should be considered when selecting the reaction conditions for a desired C–N bond formation in the course of a total synthesis or drug synthesis.

Plant Formate Dehydrogenase

Energy Technology Data Exchange (ETDEWEB)

John Markwell

2005-01-10

The research in this study identified formate dehydrogenase, an enzyme that plays a metabolic role on the periphery of one-carbon metabolism, has an unusual localization in Arabidopsis thaliana and that the enzyme has an unusual kinetic plasticity. These properties make it possible that this enzyme could be engineered to attempt to engineer plants with an improved photosynthetic efficiency. We have produced transgenic Arabidopsis and tobacco plants with increased expression of the formate dehydrogenase enzyme to initiate further studies.

Comprehensive characterisation of products from cobalt catalysed Fischer-Tropsch reaction

Energy Technology Data Exchange (ETDEWEB)

Marion, M.C.; Bertoncini, F.; Hugues, F.; Forestiere, A. [IFP, Vernaison (France)

2006-07-01

Fischer-Tropsch reaction synthesis has been studied in presence of supported cobalt catalysts. The experimental work has been performed by using a slurry pilot plant. All the gaseous and liquid products, including by-products recovered in the water phase produced, have been analysed in order to determine the whole products distribution and the catalyst selectivity. Apart from paraffin which are the main products obtained via cobalt-catalyzed Fischer-Tropsch synthesis, olefins and oxygenates by-products present also their own distribution. These detailed data are available thanks to new dedicated analytical methods developed in IFP laboratories. (orig.)

Evidence for Importance of tRNA-dependent Cytokinin Biosynthetic Pathway in the Moss Physcomitrella patens

Czech Academy of Sciences Publication Activity Database

Yevdakova, N.A.; Motyka, Václav; Malbeck, Jiří; Trávníčková, Alena; Novák, Ondřej; Strnad, Miroslav; von Schwartzenberg, K.

2008-01-01

Roč. 27, č. 3 (2008), s. 271-281 ISSN 0721-7595 R&D Projects: GA MŠk(CZ) LC06034; GA ČR GA206/05/0894; GA AV ČR IAA600380701 Institutional research plan: CEZ:AV0Z50380511 Keywords : Physcomitrella * ove mutant * Cytokinin biosynthesis * tRNA-isopentenyl transferase Subject RIV: ED - Physiology Impact factor: 2.109, year: 2008

The conserved Lysine69 residue plays a catalytic role in Mycobacterium tuberculosis shikimate dehydrogenase

Directory of Open Access Journals (Sweden)

Rodrigues Valnês

2009-01-01

Full Text Available Abstract Background The shikimate pathway is an attractive target for the development of antitubercular agents because it is essential in Mycobacterium tuberculosis, the causative agent of tuberculosis, but absent in humans. M. tuberculosis aroE-encoded shikimate dehydrogenase catalyzes the forth reaction in the shikimate pathway. Structural and functional studies indicate that Lysine69 may be involved in catalysis and/or substrate binding in M. tuberculosis shikimate dehydrogenase. Investigation of the kinetic properties of mutant enzymes can bring important insights about the role of amino acid residues for M. tuberculosis shikimate dehydrogenase. Findings We have performed site-directed mutagenesis, steady-state kinetics, equilibrium binding measurements and molecular modeling for both the wild-type M. tuberculosis shikimate dehydrogenase and the K69A mutant enzymes. The apparent steady-state kinetic parameters for the M. tuberculosis shikimate dehydrogenase were determined; the catalytic constant value for the wild-type enzyme (50 s-1 is 68-fold larger than that for the mutant K69A (0.73 s-1. There was a modest increase in the Michaelis-Menten constant for DHS (K69A = 76 μM; wild-type = 29 μM and NADPH (K69A = 30 μM; wild-type = 11 μM. The equilibrium dissociation constants for wild-type and K69A mutant enzymes are 32 (± 4 μM and 134 (± 21, respectively. Conclusion Our results show that the residue Lysine69 plays a catalytic role and is not involved in substrate binding for the M. tuberculosis shikimate dehydrogenase. These efforts on M. tuberculosis shikimate dehydrogenase catalytic mechanism determination should help the rational design of specific inhibitors, aiming at the development of antitubercular drugs.

Seasonal changes of cytokinins in upper and lower leaves of a sugar maple crown

International Nuclear Information System (INIS)

Held, M.A.; Quesnelle, P.E.; Emery, R.J.N.

2005-01-01

Although it is well accepted that cytokinins (CKs) regulate processes such as leaf senescence and stomatal conductance, data on CKs in the canopy of mature trees are lacking in the literature. Here we report the first in situ sampling for determination of CKs in mature sugar maple (Acer saccharum) canopy layers. The upper canopy showed a distinct seasonal pattern in total CK content, whereas the lower canopy remained relatively unchanged

Measurement of the enzymes lactate dehydrogenase and creatine kinase using reflectance spectroscopy and reagent strips.

OpenAIRE

Stevens, J F; Tsang, W; Newall, R G

1983-01-01

Two new methods for the assay of total activities of lactate dehydrogenase and creatine kinase are described, in which the enzyme activities are measured from a solid-state reagent strip during a kinetic reaction, the reaction being monitored in the ultra-violet region of the spectrum by reflectance spectroscopy. The performances of these methods are evaluated, and compared to conventional "wet" chemistry methods. The solid-phase reagent methods demonstrated precision and accuracy acceptable ...

Cytokinin Differences in In Vitro Cultures and Inflorescences from Normal and Mantled Oil Palm (Elaeis guineensis Jacq.)

Czech Academy of Sciences Publication Activity Database

Ooi, S. E.; Novák, Ondřej; Doležal, Karel; Ishak, Z.; Ong-Abdullah, M.

2013-01-01

Roč. 32, č. 4 (2013), s. 865-874 ISSN 0721-7595 Grant - others:GA MŠk(CZ) ED0007/01/01 Program:ED Institutional research plan: CEZ:AV0Z50380511 Keywords : Cytokinin * Elaeis guineensis * Inflorescence Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 2.058, year: 2013

Overexpression of Farnesyl Diphosphate Synthase in Arabidopsis Mitochondria Triggers Light-dependent Lesion Formation and Alters Cytokinin Homeostasis

Czech Academy of Sciences Publication Activity Database

Manzano, D.; Busquets, A.; Closa, M.; Hoyerová, Klára; Schaller, H.; Kamínek, Miroslav; Arró, M.; Ferrer, A.

2006-01-01

Roč. 61, 1-2 (2006), s. 195-213 ISSN 0167-4412 R&D Projects: GA AV ČR(CZ) IAA600380507 Institutional research plan: CEZ:AV0Z50380511 Keywords : Arabidopsis thaliana * cytokinin * farnesyl diphosphate synthase * isoprenoid Subject RIV: EF - Botanics Impact factor: 3.577, year: 2006

The Effects of Fenarimol and Methyl Parathion on Glucose 6-Phosphate Dehydrogenase Enzyme Activity in Rats

Directory of Open Access Journals (Sweden)

Ferda ARI

2017-10-01

Full Text Available Fenarimol and methyl parathion are pesticides that have been used in agriculture for several years. These pesticides have significant effects on environmental and human health. Therefore, we investigated the effects of methyl parathion and fenarimol on glucose 6-phosphate dehydrogenase (EC 1.1.1.49 enzyme activity in rats. The glucose 6- phosphate dehydrogenase is the first enzyme of the pentose phosphate pathway and it is important in detoxifying reactions by NADPH generated. In this study, wistar albino rats administrated with methyl parathion (7 mg kg–1 and fenarimol (200 mg kg−1 by intraperitoneally for different periods (2, 4, 8, 16, 32, 64, and 72 h. The glucose 6-phosphate dehydrogenase enzyme activity was assayed in liver, kidney, brain, and small intestine in male and female rats. The exposure of fenarimol and methyl parathion caused increase of glucose 6-phosphate dehydrogenase enzyme activity in rat tissues, especially at last periods. We suggest that this increment of enzyme activity may be the reason of toxic effects of fenarimol and methyl parathion.

Preparation and Characterization of Enzyme Compartments in UV-Cured Polyurethane-Based Materials and Their Application in Enzymatic Reactions

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Diana Uhrich

2017-11-01

Full Text Available The preparation and characterization of UV-cured polyurethane-based materials for the mild inclusion immobilization of enzymes was investigated. Full curing of the polymer precursor/enzyme solution mixture was realized by a short irradiation with UV-light at ambient temperatures. The included aqueous enzyme solution remains highly dispersed in the polymer material with an even size distribution throughout the polymer material. The presented concept provides stable enzyme compartments which were applied for an alcohol dehydrogenase-catalyzed reduction reaction in organic solvents. Cofactor regeneration was achieved by a substrate-coupled approach via 2-propanol or an enzyme-coupled approach by a glucose dehydrogenase. This reaction concept can also be used for a simultaneous application of contrary biocatalytic reaction conditions within an enzymatic cascade reaction. Independent polymer-based reaction compartments were provided for two incompatible enzymatic reaction systems (alcohol dehydrogenase and hydroxynitrile lyase, while the relevant reactants diffuse between the applied compartments.

Insight into the stereospecificity of short-chain thermus thermophilus alcohol dehydrogenase showing pro-S hydride transfer and prelog enantioselectivity.

Science.gov (United States)

Pennacchio, Angela; Giordano, Assunta; Esposito, Luciana; Langella, Emma; Rossi, Mosè; Raia, Carlo A

2010-04-01

The stereochemistry of the hydride transfer in reactions catalyzed by NAD(H)-dependent alcohol dehydrogenase from Thermus thermophilus HB27 was determined by means of (1)H-NMR spectroscopy. The enzyme transfers the pro-S hydrogen of [4R-(2)H]NADH and exhibits Prelog specificity. Enzyme-substrate docking calculations provided structural details about the enantioselectivity of this thermophilic enzyme. These results give additional insights into the diverse active site architectures of the largely versatile short-chain dehydrogenase superfamily enzymes. A feasible protocol for the synthesis of [4R-(2)H]NADH with high yield was also set up by enzymatic oxidation of 2-propanol-d(8) catalyzed by Bacillus stearothermophilus alcohol dehydrogenase.

Screening test for rapid food safety evaluation by menadione-catalysed chemiluminescent assay.

Science.gov (United States)

Yamashoji, Shiro; Yoshikawa, Naoko; Kirihara, Masayuki; Tsuneyoshi, Toshihiro

2013-06-15

The chemiluminescent assay of menadione-catalysed H2O2 production by living mammalian cells was proposed to be useful for rapid food safety evaluation. The tested foods were extracted with water, ethanol and dimethylsulfoxide, and each extract was incubated with NIH3T3, Neuro-2a and HepG2 cells for 4h. Menadione-catalysed H2O2 production by living mammalian cells exposed to each extract was determined by the chemiluminescent assay requiring only 10 min, and the viability of the cells was estimated as percentage based on H2O2 production by intact cells. In this study the cytotoxicity of food was rated in order of inhibitory effect on H2O2 production by intact cells. The well known natural toxins such as Fusarium mycotoxin, tomato toxin tomatine, potato toxin solanine and marine toxins terodotoxin and brevetoxin could be detected by the above chemiluminescent assay. Copyright © 2012 Elsevier Ltd. All rights reserved.

Mechanistic study of ruthenium (III) catalysed oxidation of L-lysine by ...

Indian Academy of Sciences (India)

Administrator

MS received 15 April 2008; revised 2 July 2008. Abstract. The kinetics of Ru(III) catalysed oxidation of L-lysine by diperiodatoargentate (III) (DPA) in alkaline medium at 298 K and a constant ionic strength of 0⋅50 mol dm. –3 was studied spectrophotometri- cally. The oxidation products are aldehyde (5-aminopentanal) and ...

Bioelectrochemical fuel cell and sensor based on quinoprotein alcohol dehydrogenase

Energy Technology Data Exchange (ETDEWEB)

Davis, G; Hill, H A.O.; Aston, W J; Higgins, I J; Turner, A P.F.

1983-09-01

A biofuel cell, yielding a stable and continuous low-power output, based on the enzymatic oxidation of methanol to formic acid has been designed and investigated. The homogeneous kinetics of the electrochemically-coupled enzymatic oxidation reaction were investigated and optimized. The biofuel cell also functioned as a sensitive method for the detection of primary alcohols. A method for medium-scale preparation of the enzyme alcohol dehydrogenase (alcohol: (acceptor) oxidoreductase, EC 1.1.99.8) is described. (Refs. 14).

The role of endogenous cytokinins and environmental factors in flowering in the vine cactus Hylocereus undatus

Czech Academy of Sciences Publication Activity Database

Khaimov-Armoza, A.; Novák, Ondřej; Strnad, Miroslav; Mizrahi, Y.

2012-01-01

Roč. 60, č. 3 (2012), s. 371-383 ISSN 0792-9978 R&D Projects: GA AV ČR KAN200380801 Institutional research plan: CEZ:AV0Z50380511 Keywords : cytokinins * flowering * flower induction Subject RIV: EC - Immunology Impact factor: 0.259, year: 2012 http://www.tandfonline.com/doi/abs/10.1560/IJPS.60.1.371

CHANGES IN ENDOGENOUS CYTOKININ CONCENTRATIONS IN CHLORELLA (CHLOROPHYCEAE) IN RELATION TO LIGHT AND THE CELL CYCLE

Czech Academy of Sciences Publication Activity Database

Stirk, W. A.; van Staden, J.; Novák, Ondřej; Doležal, Karel; Strnad, Miroslav; Dobrev, Petre; Sipos, G.; Oerdoeg, V.; Balint, P.

2011-01-01

Roč. 47, č. 2 (2011), s. 291-301 ISSN 0022-3646 R&D Projects: GA ČR GA301/08/1649; GA ČR GA206/09/1284 Institutional research plan: CEZ:AV0Z50380511 Keywords : cell cycle * Chlorella * cis-zeatin * cytokinins * N6-(2-isopentenyl)adenine Subject RIV: EF - Botanics Impact factor: 2.071, year: 2011

Changes in endogenous cytokinin levels in cotyledons of Cucurbita pepo (zucchini) during natural and dark-induced senescence

Czech Academy of Sciences Publication Activity Database

Ananieva, H.; Malbeck, Jiří; Kamínek, Miroslav; Staden, J.

2004-01-01

Roč. 122, č. 1 (2004), s. 133-142 ISSN 0031-9317 R&D Projects: GA ČR GA522/02/0530 Institutional research plan: CEZ:AV0Z5038910 Keywords : Cucurbita pepo L. (zucchini) * chlorophyll content * Cytokinin Subject RIV: GD - Fertilization, Irrigation, Soil Processing Impact factor: 2.017, year: 2004

Enzymatic conversion of CO2 to CH3OH via reverse dehydrogenase cascade biocatalysis: Quantitative comparison of efficiencies of immobilized enzyme systems

DEFF Research Database (Denmark)

Marpani, Fauziah Binti; Pinelo, Manuel; Meyer, Anne S.

2017-01-01

A designed biocatalytic cascade system based on reverse enzymatic catalysis by formate dehydrogenase (EC 1.2.1.2), formaldehyde dehydrogenase (EC 1.2.1.46), and alcohol dehydrogenase (EC 1.1.1.1) can convert carbon dioxide (CO2) to methanol (CH3OH) via formation of formic acid (CHOOH......) and formaldehyde (CHOH) during equimolar cofactor oxidation of NADH to NAD+. This reaction is appealing because it represents a double gain: (1) reduction of CO2 and (2) an alternative to fossil fuel based production of CH3OH. The present review evaluates the efficiency of different immobilized enzyme systems...

21 CFR 862.1670 - Sorbitol dehydrogenase test system.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Sorbitol dehydrogenase test system. 862.1670... Systems § 862.1670 Sorbitol dehydrogenase test system. (a) Identification. A sorbitol dehydrogenase test system is a device intended to measure the activity of the enzyme sorbitol dehydrogenase in serum...

Study of endogenic abscisic acids and cytokinin content in soybean crops of variable salt sensitivity as well as the effect of exogenically applied abscisic acid on Cl/sup -/ translocation. [in German

Energy Technology Data Exchange (ETDEWEB)

Roeb, G.

1981-05-01

A study of the phytohormones abscisic acid and cytokinin with respect to plant salt stress and its relationship to genetic control over endogen content. An analysis is made of the acid cytokinin content, and an investigation is made of the influence exerted by exogenic applied synthetic abscisic acid on Cl/sup -/ uptake and accumulation. 275 references, 14 figures, 11 tables.

Cytokinins and auxin communicate nitrogen availability as long-distance signal molecules in pineapple (Ananas comosus).

Science.gov (United States)

Tamaki, Vívian; Mercier, Helenice

2007-11-01

This work aimed at identifying a possible role of phytohormones in long-distance (root-shoot) signaling under nitrogen deficiency. Three-months old pineapple plants were transferred from Murashige and Skoog (MS) medium to nitrogen-free MS (-N). During the first 24h on -N, 20 plants were harvested every 4h. After 30 days in -N, the remaining plants were transferred back to regular MS (+N) and 20 plants harvested every 4h for the first 24h. Following the harvests, endogenous levels of nitrate (NO(3)(-)), indole-3-acetic acid (IAA), isopentenyladenine (iP), isopentenyladenine riboside (iPR), zeatin (Z) and zeatin riboside (ZR) were analyzed in roots and leaves. In N-starved plants, the NO(3)(-) level dropped by 20% in roots between the first (4h) and the second harvest (8h). In leaves a reduction of 20% was found 4h later. Accumulation of IAA peaked in leaves at 16h. In roots, the accumulation of IAA only started at 16h while the leaf content was already in decline, which suggests that the hormone might have traveled from the leaves to the roots, communicating N-shortage. The contents of the four cytokinins were generally low in both, shoot and roots, and remained almost unchanged during the 24h of analysis. After N re-supply, roots showed a NO(3)(-) peak at 8h whereas the foliar concentration increased 4h later. Hormone levels in roots climaxed at 8h, this coinciding with the highest NO(3)(-) concentration. In leaf tissue, a dramatic accumulation was only observed for Z and ZR, and the peak was seen 4h later than in roots, suggesting that Z-type cytokinins might have traveled from the roots to the leaves. These findings provide evidence that there is a signaling pathway for N availability in pineapple plants, communicated upwards through cytokinins (N-supplemented plants) and downwards through auxin (N-starved plants).

The Oxidative Fermentation of Ethanol in Gluconacetobacter diazotrophicus Is a Two-Step Pathway Catalyzed by a Single Enzyme: Alcohol-Aldehyde Dehydrogenase (ADHa

Directory of Open Access Journals (Sweden)

Saúl Gómez-Manzo

2015-01-01

Full Text Available Gluconacetobacter diazotrophicus is a N2-fixing bacterium endophyte from sugar cane. The oxidation of ethanol to acetic acid of this organism takes place in the periplasmic space, and this reaction is catalyzed by two membrane-bound enzymes complexes: the alcohol dehydrogenase (ADH and the aldehyde dehydrogenase (ALDH. We present strong evidence showing that the well-known membrane-bound Alcohol dehydrogenase (ADHa of Ga. diazotrophicus is indeed a double function enzyme, which is able to use primary alcohols (C2–C6 and its respective aldehydes as alternate substrates. Moreover, the enzyme utilizes ethanol as a substrate in a reaction mechanism where this is subjected to a two-step oxidation process to produce acetic acid without releasing the acetaldehyde intermediary to the media. Moreover, we propose a mechanism that, under physiological conditions, might permit a massive conversion of ethanol to acetic acid, as usually occurs in the acetic acid bacteria, but without the transient accumulation of the highly toxic acetaldehyde.

3H-labelling of belladonna alkaloids by catalysed exchange with microwave excitation

International Nuclear Information System (INIS)

Zhang Liming; Zheng Dongzhu; Yuan Jianmin; Jiang Xiaoma; Zhao Xialing

1992-01-01

The specific activities of the 3 H-labelled belladonna alkaloids obtained by catalysed exchange method with microwave excitation were 16-32 TBq/mol. More than 90% labelled positions of these 3 H-tracers were on phenyl rings. The radiochemical purity and chemical purity of crude products were both in 75-80%

Role of gibberellins and cytokinins in regulation of germination during development and ripening of Triticale caryopses

Directory of Open Access Journals (Sweden)

Stanisław Weidner

2014-01-01

Full Text Available The germination of caryopses of M-T3 Triticale generation, which were freshly harvested in different growth and developmental phases has been studied. A significant influence of the abscisic acid (ABA accumulation on the increment of number of germinating caryopses has been found. Already in the first phase af the embryogenesis considerable stimulating effects of kinetin and gibberellin-A3 (GA3 on the germination of embryos which were isolated from freshly collected grains have been shown. When both stimulators were used together marked synergetic reaction occurred. It has been also determined that in the initial period of embryogensis premature germination occurs, to a higher extent, under the action of cytokinins than! Whether in the further phases of the caryopse development, when embryo develop mainly through the cell elongation, mostly gibberellins seem to be responsible for the activation of germination processes. The more mature were seeds the quicker germinated whole caryopses and embryos isolated from them at different ripeness, after 3-month storage. The highest stimulation of germination by phytohormones has been found for the most mature caryopses. The action of gibberellic acid has been particulary strong.

Engineering the cytokinin-glucoside specificity of the maize beta-D-glucosidase Zm-p60.1 using site-directed random mutagenesis

Czech Academy of Sciences Publication Activity Database

Filipi, T.; Mazura, P.; Janda, L.; Kiran, N.S.; Brzobohatý, Břetislav

2012-01-01

Roč. 74, FEB2012 (2012), s. 40-48 ISSN 0031-9422 Institutional support: RVO:68081707 Keywords : beta-Glucosidase * cis-Zeatin-O-beta-D-glucopyranoside * Cytokinin metabolism Subject RIV: BO - Biophysics Impact factor: 3.050, year: 2012

Nitrogen metabolism and gas exchange parameters associated with zinc stress in tobacco expressing an ipt gene for cytokinin synthesis

Czech Academy of Sciences Publication Activity Database

Pavlíková, D.; Pavlík, Milan; Procházková, Dagmar; Zemanová, V.; Hnilička, F.; Wilhelmová, Naděžda

2014-01-01

Roč. 171, č. 7 (2014), s. 559-564 ISSN 0176-1617 R&D Projects: GA ČR(CZ) GAP501/11/1239 Institutional support: RVO:61389030 Keywords : Amino acid * Cytokinins * Photosynthetic rate Subject RIV: EF - Botanics Impact factor: 2.557, year: 2014

New cytokinin derivatives possess UVA and UVB photoprotective effect on human skin cells and prevent oxidative stress

Czech Academy of Sciences Publication Activity Database

Hönig, Martin; Plíhalová, Lucie; Spíchal, L.; Grúz, Jiří; Kadlecová, Alena; Voller, Jiří; Rajnochová Svobodová, A.; Vostálová, J.; Ulrichová, J.; Doležal, Karel; Strnad, Miroslav

2018-01-01

Roč. 150, APR 25 (2018), s. 946-957 ISSN 0223-5234 R&D Projects: GA MŠk(CZ) LO1204 Institutional support: RVO:61389030 Keywords : Aromatic cytokinins * Caenorhabditis elegans * Kinetin derivatives * Oxidative stress * UVA/UVB photoprotectivity Subject RIV: EB - Genetics ; Molecular Biology OBOR OECD: Biochemistry and molecular biology Impact factor: 4.519, year: 2016

Reaction of organic ytterbium derivatives with alkyl- and arylhalogenides

International Nuclear Information System (INIS)

Rybakova, L.F.; Syutkina, O.P.; Garbar, A.V.; Petrov, Eh.S.

1988-01-01

Interaction of a series of organic halogenides with organic bivalent ytterbium derivatives (like Grignard reagent, RYbX, where R=CH 3 , C 6 H 5 ; X=Br, I) under metal complex catalysis is studied. Aromatic and aliphatic ytterbium derivatives undergo a reaction of cross combination with organic iodides and bromides under catalysis by NiCl 2 (PPh 3 ) 2 and Pd(PPh 3 ) 4 complexes. Therewith organo-ytterbium compounds quantitatively react with alkyl (aryl) iodides, bromine substitution for iodine in arylhalogenides results in decrease of yield of cross-combination products. Reactions of organo-ytterbium compounds with organic halogenides are more effectively catalysed by nickel complexes than by palladium ones

Cytokinins and coconut water promoted abnormalities in zygotic embryo culture of oil palm

Directory of Open Access Journals (Sweden)

Suhaimine Chaemalee

2011-12-01

Full Text Available Induction of adventitious shoot formation from mature zygotic embryo of oil palm was carried out in liquid MS mediumsupplemented with various types of cytokinins. Kinetin (KN alone at concentration of 0.5 mg/l gave the highest adventitiousshoot formation at 13.4%. However, abnormal shoots in form of inflorescence-like structure (ILS were obtained in 5mg/l KN containing medium. For coconut water a big ILSs were formed at 10.6%. Histological studied revealed that thoseinflorescences had no clear floral organs.

Organosilane oxidation by water catalysed by large gold nanoparticles in a membrane reactor

NARCIS (Netherlands)

Gitis, V.; Beerthuis, R.; Shiju, N.R.; Rothenberg, G.

2014-01-01

We show that gold nanoparticles catalyse the oxidation of organosilanes using water as oxidant at ambient conditions. Remarkably, monodispersions of small gold particles (3.5 nm diameter) and large ones (6-18 nm diameter) give equally good conversion rates. This is important because separating large

Asymmetric reduction of ketones and β-keto esters by (S)-1-phenylethanol dehydrogenase from denitrifying bacterium Aromatoleum aromaticum.

Science.gov (United States)

Dudzik, A; Snoch, W; Borowiecki, P; Opalinska-Piskorz, J; Witko, M; Heider, J; Szaleniec, M

2015-06-01

Enzyme-catalyzed enantioselective reductions of ketones and keto esters have become popular for the production of homochiral building blocks which are valuable synthons for the preparation of biologically active compounds at industrial scale. Among many kinds of biocatalysts, dehydrogenases/reductases from various microorganisms have been used to prepare optically pure enantiomers from carbonyl compounds. (S)-1-phenylethanol dehydrogenase (PEDH) was found in the denitrifying bacterium Aromatoleum aromaticum (strain EbN1) and belongs to the short-chain dehydrogenase/reductase family. It catalyzes the stereospecific oxidation of (S)-1-phenylethanol to acetophenone during anaerobic ethylbenzene mineralization, but also the reverse reaction, i.e., NADH-dependent enantioselective reduction of acetophenone to (S)-1-phenylethanol. In this work, we present the application of PEDH for asymmetric reduction of 42 prochiral ketones and 11 β-keto esters to enantiopure secondary alcohols. The high enantioselectivity of the reaction is explained by docking experiments and analysis of the interaction and binding energies of the theoretical enzyme-substrate complexes leading to the respective (S)- or (R)-alcohols. The conversions were carried out in a batch reactor using Escherichia coli cells with heterologously produced PEDH as whole-cell catalysts and isopropanol as reaction solvent and cosubstrate for NADH recovery. Ketones were converted to the respective secondary alcohols with excellent enantiomeric excesses and high productivities. Moreover, the progress of product formation was studied for nine para-substituted acetophenone derivatives and described by neural network models, which allow to predict reactor behavior and provides insight on enzyme reactivity. Finally, equilibrium constants for conversion of these substrates were derived from the progress curves of the reactions. The obtained values matched very well with theoretical predictions.

A simple thermometric technique for reaction-rate determination of inorganic species, based on the iodide-catalysed cerium(IV)-arsenic(III) reaction.

Science.gov (United States)

Grases, F; Forteza, R; March, J G; Cerda, V

1985-02-01

A very simple reaction-rate thermometric technique is used for determination of iodide (5-20 ng ml ), based on its catalytic action on the cerium(IV)-arsenic(III) reaction, and for determination of mercury(II) (1.5-10 ng ml ) and silver(I) (2-10 ng ml ), based on their inhibitory effect on this reaction. The reaction is followed by measuring the rate of temperature increase. The method suffers from very few interferences and is applied to determination of iodide in biological and inorganic samples, and Hg(II) and Ag(I) in pharmaceutical products.

Arabidopsis ROCK1 transports UDP-GlcNAc/UDP-GalNAc and regulates ER protein quality control and cytokinin activity

Czech Academy of Sciences Publication Activity Database

Niemann, M.C.E.; Bartrina, I.; Ashikov, A.; Weber, H.; Novák, Ondřej; Spíchal, Lukáš; Strnad, Miroslav; Strasser, R.; Bakker, H.; Schmülling, T.; Werner, T.

2015-01-01

Roč. 112, č. 1 (2015), s. 291-296 ISSN 0027-8424 R&D Projects: GA MŠk LK21306; GA MŠk(CZ) LO1204 Institutional support: RVO:61389030 Keywords : ROCK1 * cytokinin * CKX Subject RIV: EF - Botanics Impact factor: 9.423, year: 2015

The influence of adsorbate interactions on elementary reaction kinetics : CO with NO, N, O, or H on Rh(100)

NARCIS (Netherlands)

Jansen, M.M.M.

2010-01-01

The kinetics of heterogeneously catalysed reactions is often described by highly simplified models. For example, the reacting adsorbates occupy one kind of site, surfaces do not reconstruct and lateral interactions between adsorbates are often neglected. Particularly the latter is only allowed for

Metabolic changes and associated cytokinin signals in response to nitrate assimilation in roots and shoots of Lolium perenne

Czech Academy of Sciences Publication Activity Database

Roche, J.; Love, J.; Guo, Q.; Song, J.C.; Cao, M.; Fraser, K.; Huege, J.; Jones, C.; Novák, Ondřej; Turnbull, M.; Jameson, P. E.

2016-01-01

Roč. 156, č. 4 (2016), s. 497-511 ISSN 0031-9317 R&D Projects: GA MŠk(CZ) LO1204; GA MŠk LK21306 Institutional support: RVO:61389030 Keywords : ZEATIN-TYPE CYTOKININS * FRUCTAN METABOLISM * USE EFFICIENCY Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.330, year: 2016

Phytohormone Involvement in the Ustilago maydis- Zea mays Pathosystem: Relationships between Abscisic Acid and Cytokinin Levels and Strain Virulence in Infected Cob Tissue.

Directory of Open Access Journals (Sweden)

Erin N Morrison

Full Text Available Ustilago maydis is the causative agent of common smut of corn. Early studies noted its ability to synthesize phytohormones and, more recently these growth promoting substances were confirmed as cytokinins (CKs. Cytokinins comprise a group of phytohormones commonly associated with actively dividing tissues. Lab analyses identified variation in virulence between U. maydis dikaryon and solopathogen infections of corn cob tissue. Samples from infected cob tissue were taken at sequential time points post infection and biochemical profiling was performed using high performance liquid chromatography-electrospray ionization tandem mass spectrometry (HPLC-ESI MS/MS. This hormone profiling revealed that there were altered levels of ABA and major CKs, with a marked reduction in CK glucosides, increases in methylthiol CKs and a particularly dramatic increase in cisZ CK forms, in U. maydis infected tissue. These changes were more pronounced in the more virulent dikaryon relative to the solopathogenic strain suggesting a role for cytokinins in moderating virulence during biotrophic infection. These findings highlight the fact that U. maydis does not simply mimic a fertilized seed but instead reprograms the host tissue. Results underscore the suitability of the Ustilago maydis- Zea mays model as a basis for investigating the control of phytohormone dynamics during biotrophic infection of plants.

Effects of 24-epibrassinolide and green light on plastid gene transcription and cytokinin content of barley leaves

Czech Academy of Sciences Publication Activity Database

Efimova, N.V.; Vaňková, Radomíra; Kusnetsov, V.; Litvinovskaya, R. P.; Zlobin, Y.L.; Dobrev, Petre; Vedenicheva, N.P.; Savchuk, A. L.; Karnachuk, R. A.; Kudryakova, N.V.; Kuznetsov, V. D.

2017-01-01

Roč. 120, APR (2017), s. 32-40 ISSN 0039-128X Institutional support: RVO:61389030 Keywords : lupinus-luteus cotyledons * arabidopsis-thaliana * de-etiolation * abscisic-acid * brassinosteroid biosynthesis * plant development * hormonal balance * mutant * expression * growth * Brassinosteroids * Cytokinin * Gene expression * Green light * Hordeum vulgare * Transcription Subject RIV: EF - Botanics OBOR OECD: Plant sciences, botany Impact factor: 2.282, year: 2016

Radiorestoration properties of several cytokinin-like substances on the normal tissues of Jerusalem artichoke treated by Co60 gamma-rays

International Nuclear Information System (INIS)

Jonard, Robert; Bayonove, Jacqueline

1976-01-01

6 cytokinin-like substances, particularly zeatin and isopentenyladenin (IPA) contained in yeast extract and their RNA prove to be effective radiorestorative agents on Jerusalem artichoke tissues cultivated in vitro; and their restorative activity is greater than that of kinetin [fr

A novel inhibitor of cytokinin degradation (INCYDE) influences the biochemical parameters and photosynthetic apparatus in NaCl-stressed tomato plants

Czech Academy of Sciences Publication Activity Database

Aremu, A.O.; Masondo, N.A.; Sunmonu, T.O.; Kulkarni, M. G.; Zatloukal, Marek; Spíchal, Lukáš; Doležal, Karel; van Staden, J.

2014-01-01

Roč. 240, č. 4 (2014), s. 877-889 ISSN 0032-0935 R&D Projects: GA MŠk(CZ) LO1204 Institutional support: RVO:61389030 Keywords : Antioxidant * Cytokinins * Chlorophyll Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.263, year: 2014

Sn-Beta zeolites with borate salts catalyse the epimerization of carbohydrates via an intramolecular carbon shift

Science.gov (United States)

Gunther, William R.; Wang, Yuran; Ji, Yuewei; Michaelis, Vladimir K.; Hunt, Sean T.; Griffin, Robert G.; Román-Leshkov, Yuriy

2012-01-01

Carbohydrate epimerization is an essential technology for the widespread production of rare sugars. In contrast to other enzymes, most epimerases are only active on sugars substituted with phosphate or nucleotide groups, thus drastically restricting their use. Here we show that Sn-Beta zeolite in the presence of sodium tetraborate catalyses the selective epimerization of aldoses in aqueous media. Specifically, a 5 wt% aldose (for example, glucose, xylose or arabinose) solution with a 4:1 aldose:sodium tetraborate molar ratio reacted with catalytic amounts of Sn-Beta yields near-equilibrium epimerization product distributions. The reaction proceeds by way of a 1,2 carbon shift wherein the bond between C-2 and C-3 is cleaved and a new bond between C-1 and C-3 is formed, with C-1 moving to the C-2 position with an inverted configuration. This work provides a general method of performing carbohydrate epimerizations that surmounts the main disadvantages of current enzymatic and inorganic processes. PMID:23047667

Phloem development in nematode-induced feeding sites: The implications of auxin and cytokinin

Directory of Open Access Journals (Sweden)

Birgit eAbsmanner

2013-07-01

Full Text Available Sedentary plant parasitic nematodes such as root-knot nematodes and cyst nematodes induce giant cells or syncytia, respectively, in their host plant’s roots. These highly specialized structures serve as feeding sites from which exclusively the nematodes withdraw nutrients. While giant cells are symplastically isolated and obtain assimilates by transporter-mediated processes syncytia are massively connected to the phloem by plasmodesmata. To support the feeding sites and the nematode during their development, phloem is induced around syncytia and giant cells. In the case of syncytia the unloading phloem consists of sieve elements and companion cells and in the case of root knots it consists exclusively of sieve elements. We applied immunohistochemistry to identify the cells within the developing phloem that responded to auxin and cytokinin. Both feeding sites themselves did not respond to either hormone. We were able to show that in root knots an auxin response precedes the differentiation of these auxin responsive cells into phloem elements. This process appears to be independent of B-type Arabidopsis response regulators. Using additional markers for tissue identity we provide evidence that around giant cells protophloem is formed and proliferates dramatically. In contrast, the phloem around syncytia responded to both hormones. The presence of companion cells as well as hormone-responsive sieve elements suggests that metaphloem development occurs. The implication of auxin and cytokinin in the further development of the metaphloem is discussed.

O-Alkyl Hydroxamates as Metaphors of Enzyme-Bound Enolate Intermediates in Hydroxy Acid Dehydrogenases. Inhibitors of Isopropylmalate Dehydrogenase, Isocitrate Dehydrogenase, and Tartrate Dehydrogenase(1).

Science.gov (United States)

Pirrung, Michael C.; Han, Hyunsoo; Chen, Jrlung

1996-07-12

The inhibition of Thermus thermophilus isopropylmalate dehydrogenase by O-methyl oxalohydroxamate was studied for comparison to earlier results of Schloss with the Salmonella enzyme. It is a fairly potent (1.2 &mgr;M), slow-binding, uncompetitive inhibitor against isopropylmalate and is far superior to an oxamide (25 mM K(i) competitive) that is isosteric with the ketoisocaproate product of the enzyme. This improvement in inhibition was attributed to its increased NH acidity, which presumably is due to the inductive effect of the hydroxylamine oxygen. This principle was extended to the structurally homologous enzyme isocitrate dehydrogenase from E. coli, for which the compound O-(carboxymethyl) oxalohydroxamate is a 30 nM inhibitor, uncompetitive against isocitrate. The pH dependence of its inhibition supports the idea that it is bound to the enzyme in the anionic form. Another recently discovered homologous enzyme, tartrate dehydrogenase from Pseudomonas putida, was studied with oxalylhydroxamate. It has a relatively low affinity for the enzyme, though it is superior to tartrate. On the basis of these leads, squaric hydroxamates with increased acidity compared to squaric amides directed toward two of these enzymes were prepared, and they also show increased inhibitory potency, though not approaching the nanomolar levels of the oxalylhydroxamates.

Cytokinin induced shoot regeneration and flowering of Scoparia dulcis L. (Scrophulariaceae)-an ethnomedicinal herb.

Science.gov (United States)

Premkumar, G; Sankaranarayanan, R; Jeeva, S; Rajarathinam, K

2011-06-01

To develop an improved protocol for micropropagation of ethnomedicinally important Scoparia dulcis (S. dulcis) L. Explants were inoculated on MS basal medium supplemented with kinetin and 6-benzylaminopurine for shoot bud induction. To enhance the shoot induction, various auxins like 3-indoleacetic acid or 3-indolebutyric acid or α-naphthylacetic acid were tested along with 2.32 M KI and 4.44 µM BAP. The regenerated shoots were rooted in half strength MS medium supplemented with various concentrations of IAA, IBA or NAA. After roots were developed, the plantlets were transplanted to pots filled with vermiculate and sand and kept in growth chamber with 70%-80% humidity under 16 h photoperiod. After acclimatization, the plantlets were transferred to the garden and survival percentage was calculated. Data were statistically analyzed and means were compared using Duncan's multiple range test (Pdulcis. Shoot induction on young leaf explants was most successful in MS medium supplemented with combination of two cytokinins (2.32 µM KI and 4.44 µM BAP) 2.85 µM IAA, 10% CM and 1 483.79 µM adenine sulfate. A single young leaf explant was capable of producing 59 shoots after 13 days of culture. Flower was induced in medium supplemented with combination of KI and BAP. Cytokinins are the key factor to induce the direct shoot regeneration and flowering of S. dulcis.

Structural and Thermodynamic Basis for Weak Interactions between Dihydrolipoamide Dehydrogenase and Subunit-binding Domain of the Branched-chain [alpha]-Ketoacid Dehydrogenase Complex

Energy Technology Data Exchange (ETDEWEB)

Brautigam, Chad A.; Wynn, R. Max; Chuang, Jacinta L.; Naik, Mandar T.; Young, Brittany B.; Huang, Tai-huang; Chuang, David T. (AS); (UTSMC)

2012-02-27

The purified mammalian branched-chain {alpha}-ketoacid dehydrogenase complex (BCKDC), which catalyzes the oxidative decarboxylation of branched-chain {alpha}-keto acids, is essentially devoid of the constituent dihydrolipoamide dehydrogenase component (E3). The absence of E3 is associated with the low affinity of the subunit-binding domain of human BCKDC (hSBDb) for hE3. In this work, sequence alignments of hSBDb with the E3-binding domain (E3BD) of the mammalian pyruvate dehydrogenase complex show that hSBDb has an arginine at position 118, where E3BD features an asparagine. Substitution of Arg-118 with an asparagine increases the binding affinity of the R118N hSBDb variant (designated hSBDb*) for hE3 by nearly 2 orders of magnitude. The enthalpy of the binding reaction changes from endothermic with the wild-type hSBDb to exothermic with the hSBDb* variant. This higher affinity interaction allowed the determination of the crystal structure of the hE3/hSBDb* complex to 2.4-{angstrom} resolution. The structure showed that the presence of Arg-118 poses a unique, possibly steric and/or electrostatic incompatibility that could impede E3 interactions with the wild-type hSBDb. Compared with the E3/E3BD structure, the hE3/hSBDb* structure has a smaller interfacial area. Solution NMR data corroborated the interactions of hE3 with Arg-118 and Asn-118 in wild-type hSBDb and mutant hSBDb*, respectively. The NMR results also showed that the interface between hSBDb and hE3 does not change significantly from hSBDb to hSBDb*. Taken together, our results represent a starting point for explaining the long standing enigma that the E2b core of the BCKDC binds E3 far more weakly relative to other {alpha}-ketoacid dehydrogenase complexes.

Catalytic properties of thermophilic lactate dehydrogenase and halophilic malate dehydrogenase at high temperature and low water activity.

Science.gov (United States)

Hecht, K; Wrba, A; Jaenicke, R

1989-07-15

Thermophilic lactate dehydrogenases from Thermotoga maritima and Bacillus stearothermophilus are stable up to temperature limits close to the optimum growth temperature of their parent organisms. Their catalytic properties are anomalous in that Km shows a drastic increase with increasing temperature. At low temperatures, the effect levels off. Extreme halophilic malate dehydrogenase from Halobacterium marismortui exhibits a similar anomaly. Increasing salt concentration (NaCl) leads to an optimum curve for Km, oxaloacctate while Km, NADH remains constant. Previous claims that the activity of halophilic malate dehydrogenase shows a maximum at 1.25 M NaCl are caused by limiting substrate concentration; at substrate saturation, specific activity of halophilic malate dehydrogenase reaches a constant value at ionic strengths I greater than or equal to 1 M. Non-halophilic (mitochondrial) malate dehydrogenase shows Km characteristics similar to those observed for the halophilic enzyme. The drastic decrease in specific activity of the mitochondrial enzyme at elevated salt concentrations is caused by the salt-induced increase in rigidity of the enzyme, rather than gross structural changes.

cis-chlorobenzene dihydrodiol dehydrogenase (TcbB) from Pseudomonas sp. strain P51, expressed in Escherichia coli DH5alpha(pTCB149), catalyzes enantioselective dehydrogenase reactions.

Science.gov (United States)

Raschke, H; Fleischmann, T; Van Der Meer, J R; Kohler, H P

1999-12-01

cis-Chlorobenzene dihydrodiol dehydrogenase (CDD) from Pseudomonas sp. strain P51, cloned into Escherichia coli DH5alpha(pTCB149) was able to oxidize cis-dihydrodihydroxy derivatives (cis-dihydrodiols) of dihydronaphthalene, indene, and four para-substituted toluenes to the corresponding catechols. During the incubation of a nonracemic mixture of cis-1,2-indandiol, only the (+)-cis-(1R,2S) enantiomer was oxidized; the (-)-cis-(S,2R) enantiomer remained unchanged. CDD oxidized both enantiomers of cis-1,2-dihydroxy-1,2,3, 4-tetrahydronaphthalene, but oxidation of the (+)-cis-(1S,2R) enantiomer was delayed until the (-)-cis-(1R,2S) enantiomer was completely depleted. When incubated with nonracemic mixtures of para-substituted cis-toluene dihydrodiols, CDD always oxidized the major enantiomer at a higher rate than the minor enantiomer. When incubated with racemic 1-indanol, CDD enantioselectively transformed the (+)-(1S) enantiomer to 1-indanone. This stereoselective transformation shows that CDD also acted as an alcohol dehydrogenase. Additionally, CDD was able to oxidize (+)-cis-(1R,2S)-dihydroxy-1, 2-dihydronaphthalene, (+)-cis-monochlorobiphenyl dihydrodiols, and (+)-cis-toluene dihydrodiol to the corresponding catechols.

cis-Chlorobenzene Dihydrodiol Dehydrogenase (TcbB) from Pseudomonas sp. Strain P51, Expressed in Escherichia coli DH5α(pTCB149), Catalyzes Enantioselective Dehydrogenase Reactions

Science.gov (United States)

Raschke, Henning; Fleischmann, Thomas; Van Der Meer, Jan Roelof; Kohler, Hans-Peter E.

1999-01-01

cis-Chlorobenzene dihydrodiol dehydrogenase (CDD) from Pseudomonas sp. strain P51, cloned into Escherichia coli DH5α(pTCB149) was able to oxidize cis-dihydrodihydroxy derivatives (cis-dihydrodiols) of dihydronaphthalene, indene, and four para-substituted toluenes to the corresponding catechols. During the incubation of a nonracemic mixture of cis-1,2-indandiol, only the (+)-cis-(1R,2S) enantiomer was oxidized; the (−)-cis-(S,2R) enantiomer remained unchanged. CDD oxidized both enantiomers of cis-1,2-dihydroxy-1,2,3,4-tetrahydronaphthalene, but oxidation of the (+)-cis-(1S,2R) enantiomer was delayed until the (−)-cis-(1R,2S) enantiomer was completely depleted. When incubated with nonracemic mixtures of para-substituted cis-toluene dihydrodiols, CDD always oxidized the major enantiomer at a higher rate than the minor enantiomer. When incubated with racemic 1-indanol, CDD enantioselectively transformed the (+)-(1S) enantiomer to 1-indanone. This stereoselective transformation shows that CDD also acted as an alcohol dehydrogenase. Additionally, CDD was able to oxidize (+)-cis-(1R,2S)-dihydroxy-1,2-dihydronaphthalene, (+)-cis-monochlorobiphenyl dihydrodiols, and (+)-cis-toluene dihydrodiol to the corresponding catechols. PMID:10583971

Cis-Chlorobenzene dihydrodiol dehydrogenase (TcbB) from Pseudomonas sp. strain P51, expressed in Escherichia coli DH5{alpha}(pTCB149), catalyzes enantioselective dehydrogenase reactions

Energy Technology Data Exchange (ETDEWEB)

Raschke, H.; Fleischmann, T.; Meer, J.R. van der; Kohler, H.P.E.

1999-12-01

cis-Chlorobenzene dihydrodiol dehydrogenase (CDD) from Pseudomonas sp. strain P51, cloned into Escherichia coli DH5{alpha}(pTCB149) was able to oxidize cis-dihydrodihydroxy derivatives (cis-dihydrodiols) of dihydronaphthalene, indene, and four para-substituted toluenes to the corresponding catechols. During the incubation of a nonracemic mixture of cis-1,2-indandiol, only the (+)-cis-(1R,2S) enantiomer was oxidized; the (-)-cis-(S,2R) enantiomer remained unchanged, CDD oxidized both enantiomers of cis-1,2-dihydroxy-1,2,3,4-tetrahydronaphthalene, but oxidation of the (+)-cis-(1S,2R) enantiomer was delayed until the (-)-cis-(1R,2S) enantiomer was completely depleted. When incubated with nonracemic mixtures of para-substituted cis-toluene dihydrodiols, CDD always oxidized the major enantiomer at a higher rate than the minor enantiomer. When incubated with racemic 1-indanol, CDD enantioselectively transformed the (+)-(1S) enatiomer to 1-indanone. This stereoselective transformation shows that CDD also acted as an alcohol dehydrogenase. Additionally, CDD was able to oxidize (+)-cis-(1R,2S)-dihydroxy-1,2-dihydronaphthalene, (+)-cis-monochlorobiphenyl dihydrodiols, and (+)-cis-toluene dihydrodiol to the corresponding catechols.

Genetics Home Reference: dihydropyrimidine dehydrogenase deficiency

Science.gov (United States)

... 5-fluorouracil and capecitabine. These drugs are not broken down efficiently by people with dihydropyrimidine dehydrogenase deficiency ... of this enzyme. Because fluoropyrimidine drugs are also broken down by the dihydropyrimidine dehydrogenase enzyme, deficiency of ...

Biodiesel Derive Bio-oil of Hermetia illucens Pre-pupae Catalysed by Sulphonated Biochar

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Leong Siew Yoong

2018-01-01

Full Text Available This study investigates the development of biochar catalyst from bamboo applied for biodiesel synthesis. A non-conventional biodiesel feedstock was used in the in-situ transesterification reaction. This non-conventional feedstock is obtained from an insect’s fly, the Hermetia illucens fly. Biochar derived from bamboo has been investigated as a promising catalyst for biodiesel synthesis. The biochar acid catalysts were prepared by sulphonation via impregnation with concentrated sulphuric acid. The prepared catalysts were investigated for their performance to catalyse in-situ transesterification via ultra-sonication of Hermetia illucens bio-oil. The effects of carbonisation time (1 hour and 2 hour and temperature (400°C, 500°C and 600°C as well as catalyst loading (5-20 wt% on oil basis on the transesterification yield were studied. Result showed that the highest yield of FAME obtained was 95.6% with catalyst loading of 15 wt% carbonized at 500°C for 2 hours. Sharp band of methyl ester functional groups were observed in the FTIR spectra at 1735-1750cm-1. The composition of this methyl ester was further deduced using gas chromatography and the fatty acid was predominantly lauric acid.

Biodiesel Derive Bio-oil of Hermetia illucens Pre-pupae Catalysed by Sulphonated Biochar

Science.gov (United States)

Yoong Leong, Siew; Chong, Soo Shin; Chin, Kah Seng

2018-03-01

This study investigates the development of biochar catalyst from bamboo applied for biodiesel synthesis. A non-conventional biodiesel feedstock was used in the in-situ transesterification reaction. This non-conventional feedstock is obtained from an insect's fly, the Hermetia illucens fly. Biochar derived from bamboo has been investigated as a promising catalyst for biodiesel synthesis. The biochar acid catalysts were prepared by sulphonation via impregnation with concentrated sulphuric acid. The prepared catalysts were investigated for their performance to catalyse in-situ transesterification via ultra-sonication of Hermetia illucens bio-oil. The effects of carbonisation time (1 hour and 2 hour) and temperature (400°C, 500°C and 600°C) as well as catalyst loading (5-20 wt% on oil basis) on the transesterification yield were studied. Result showed that the highest yield of FAME obtained was 95.6% with catalyst loading of 15 wt% carbonized at 500°C for 2 hours. Sharp band of methyl ester functional groups were observed in the FTIR spectra at 1735-1750cm-1. The composition of this methyl ester was further deduced using gas chromatography and the fatty acid was predominantly lauric acid.

Topolins and hydroxylated thidiazuron derivatives are substrates of cytokinin O-glucosyltransferase with position specificity related to receptor recognition

Czech Academy of Sciences Publication Activity Database

Mok, M. C.; Martin, R. C.; Dobrev, Petre; Vaňková, Radomíra; Yonekura-Sakakibara, K.; Sakakibara, H.; Mok, D. W. S.

2005-01-01

Roč. 137, č. 3 (2005), s. 1057-1066 ISSN 0032-0889 R&D Projects: GA ČR GA522/04/0549; GA MŠk ME 406 Institutional research plan: CEZ:AV0Z50380511 Keywords : ARABIDOPSIS-THALIANA * AROMATIC CYTOKININS * PHASEOLUS-VULGARIS Subject RIV: EF - Botanics Impact factor: 6.114, year: 2005

Measurement of the enzymes lactate dehydrogenase and creatine kinase using reflectance spectroscopy and reagent strips.

Science.gov (United States)

Stevens, J F; Tsang, W; Newall, R G

1983-01-01

Two new methods for the assay of total activities of lactate dehydrogenase and creatine kinase are described, in which the enzyme activities are measured from a solid-state reagent strip during a kinetic reaction, the reaction being monitored in the ultra-violet region of the spectrum by reflectance spectroscopy. The performances of these methods are evaluated, and compared to conventional "wet" chemistry methods. The solid-phase reagent methods demonstrated precision and accuracy acceptable for diagnostic purposes, and were easy to use by trained operators. PMID:6655069

Changes in cytokinins are sufficient to alter developmental patterns of defense metabolites in Nicotiana attenuata

Czech Academy of Sciences Publication Activity Database

Bruetting, C.; Schaefer, N.; Vaňková, Radomíra; Gase, K.; Baldwin, I.T.; Meldau, S.

2017-01-01

Roč. 89, č. 1 (2017), s. 15-30 ISSN 0960-7412 R&D Projects: GA MŠk LD14120 Institutional support: RVO:61389030 Keywords : proteinase-inhibitor production * plant defense * arabidopsis-thaliana * leaf senescence * insect interactions * tobacco plants * jasmonic acid * manduca-sexta * cis-zeatin * responses * cytokinins * optimal defense * herbivores * inducible defense * Nicotiana attenuata * Manduca sexta * plant development * immunosenescence * phytohormones Subject RIV: ED - Physiology OBOR OECD: Plant sciences, botany Impact factor: 5.901, year: 2016

Volatile compounds emitted by diverse phytopathogenic microorganisms promote plant growth and flowering through cytokinin action

Czech Academy of Sciences Publication Activity Database

Sanchez-Lopez, A.; Baslam, M.; De Diego, N.; Jose Munoz, F.; Bahaji, A.; Almagro, G.; Ricarte-Bermejo, A.; Garcia-Gomez, P.; Li, J.; Humplík, J.F.; Novák, Ondřej; Spíchal, L.; Doležal, Karel; Baroja-Fernandez, E.; Pozueta-Romero, J.

2016-01-01

Roč. 39, č. 12 (2016), s. 2592-2608 ISSN 0140-7791 R&D Projects: GA MŠk(CZ) LO1204 Institutional support: RVO:61389030 Keywords : exceptionally high-levels * tandem mass-spectrometry * arabidopsis-thaliana * nitric-oxide * bacterial volatiles * floral transition * anthocyanin biosynthesis * transgenic arabidopsis * liquid-chromatography * organic-compounds * cytokinin * flowering * growth promotion * microbial volatile compounds * photoregulation * photosynthesis * plant-microbe interaction * starch Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 6.173, year: 2016

Optimisation and Characterisation of Lipase-Catalysed Synthesis of a Kojic Monooleate Ester in a Solvent-Free System by Response Surface Methodology.

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Khairulazhar Jumbri

Full Text Available Kojic acid is widely used to inhibit the browning effect of tyrosinase in cosmetic and food industries. In this work, synthesis of kojic monooleate ester (KMO was carried out using lipase-catalysed esterification of kojic acid and oleic acid in a solvent-free system. Response Surface Methodology (RSM based on central composite rotatable design (CCRD was used to optimise the main important reaction variables, such as enzyme amount, reaction temperature, substrate molar ratio, and reaction time along with immobilised lipase from Candida Antarctica (Novozym 435 as a biocatalyst. The RSM data indicated that the reaction temperature was less significant in comparison to other factors for the production of a KMO ester. By using this statistical analysis, a quadratic model was developed in order to correlate the preparation variable to the response (reaction yield. The optimum conditions for the enzymatic synthesis of KMO were as follows: an enzyme amount of 2.0 wt%, reaction temperature of 83.69°C, substrate molar ratio of 1:2.37 (mmole kojic acid:oleic acid and a reaction time of 300.0 min. Under these conditions, the actual yield percentage obtained was 42.09%, which is comparably well with the maximum predicted value of 44.46%. Under the optimal conditions, Novozym 435 could be reused for 5 cycles for KMO production percentage yield of at least 40%. The results demonstrated that statistical analysis using RSM can be used efficiently to optimise the production of a KMO ester. Moreover, the optimum conditions obtained can be applied to scale-up the process and minimise the cost.

Optimisation and Characterisation of Lipase-Catalysed Synthesis of a Kojic Monooleate Ester in a Solvent-Free System by Response Surface Methodology.

Science.gov (United States)

Jumbri, Khairulazhar; Al-Haniff Rozy, Mohd Fahruddin; Ashari, Siti Efliza; Mohamad, Rosfarizan; Basri, Mahiran; Fard Masoumi, Hamid Reza

2015-01-01

Kojic acid is widely used to inhibit the browning effect of tyrosinase in cosmetic and food industries. In this work, synthesis of kojic monooleate ester (KMO) was carried out using lipase-catalysed esterification of kojic acid and oleic acid in a solvent-free system. Response Surface Methodology (RSM) based on central composite rotatable design (CCRD) was used to optimise the main important reaction variables, such as enzyme amount, reaction temperature, substrate molar ratio, and reaction time along with immobilised lipase from Candida Antarctica (Novozym 435) as a biocatalyst. The RSM data indicated that the reaction temperature was less significant in comparison to other factors for the production of a KMO ester. By using this statistical analysis, a quadratic model was developed in order to correlate the preparation variable to the response (reaction yield). The optimum conditions for the enzymatic synthesis of KMO were as follows: an enzyme amount of 2.0 wt%, reaction temperature of 83.69°C, substrate molar ratio of 1:2.37 (mmole kojic acid:oleic acid) and a reaction time of 300.0 min. Under these conditions, the actual yield percentage obtained was 42.09%, which is comparably well with the maximum predicted value of 44.46%. Under the optimal conditions, Novozym 435 could be reused for 5 cycles for KMO production percentage yield of at least 40%. The results demonstrated that statistical analysis using RSM can be used efficiently to optimise the production of a KMO ester. Moreover, the optimum conditions obtained can be applied to scale-up the process and minimise the cost.

Phosphorylation site on yeast pyruvate dehydrogenase complex

International Nuclear Information System (INIS)

Uhlinger, D.J.

1986-01-01

The pyruvate dehydrogenase complex was purified to homogeneity from baker's yeast (Saccharomyces cerevisiae). Yeast cells were disrupted in a Manton-Gaulin laboratory homogenizer. The pyruvate dehydrogenase complex was purified by fractionation with polyethylene glycol, isoelectric precipitation, ultracentrifugation and chromatography on hydroxylapatite. Final purification of the yeast pyruvate dehydrogenase complex was achieved by cation-exchange high pressure liquid chromatography (HPLC). No endogenous pyruvate dehydrogenase kinase activity was detected during the purification. However, the yeast pyruvate dehydrogenase complex was phosphorylated and inactivated with purified pyruvate dehydrogenase kinase from bovine kidney. Tryptic digestion of the 32 P-labeled complex yielded a single phosphopeptide which was purified to homogeniety. The tryptic digest was subjected to chromatography on a C-18 reverse phase HPLC column with a linear gradient of acetonitrile. Radioactive fractions were pooled, concentrated, and subjected to anion-exchange HPLC. The column was developed with a linear gradient of ammonium acetate. Final purification of the phosphopeptide was achieved by chromatography on a C-18 reverse phase HPLC column developed with a linear gradient of acetonitrile. The amino acid sequence of the homogeneous peptide was determined by manual modified Edman degradation

Condensed tannins. Base-catalysed reactions of polymeric procyanidins with phloroglucinol: Intramolecular rearrangements

Science.gov (United States)

Peter E. Laks; Richard W. Hemingway; Anthony H. Conner

1987-01-01

Reactions of polymeric procyanidins with phloroglucinol at pH 12.0 and temperatures of 23 or 50°C gave epicatechin-(4β)-phloroglucinol (7), by cleavage of the interflavanoid bond between procyanidin units with subsequent addition of phloroglucinol, and (+)-catechin from the terminal unit. The phloroglucinol adduct (7) rearranged to an enolic form of 8-(3,4-...

The utilization of leftover as acid catalyst to catalyse the transesterification and esterification reactions

Science.gov (United States)

Leung, K. K.; Yau, Y. H.

2017-08-01

Biodiesel (Fatty Acid Methyl Ester, FAME) is a green and renewable energy. It is carbon neutral and produces less air pollutants in combustion. In my project, the selected feedstock of biodiesel production is grease trap oil (GTO). It is extracted from restaurants, and needs pre-treatment. The triglycerides and free fatty acid (FFA) are the main components of GTO. Both triglycerides and free fatty acid can be converted to biodiesel (Fatty Acid Methyl Ester) by transesterification and esterification, through reaction with alcohol (methanol) and catalyst. In the processes, acidic catalyst is chosen to speed up the reactions. The catalyst used In the study, a heterogeneous solid acid is applied. It is waste cooked rice (WCR) collected from leftover. The WCR powder is pyrolysed in 400°C furnace 15 hours and blown with nitrogen gas (incomplete carbonization). The WCR black powder is then mixed with concentrated sulphuric acid and heat in 160°C furnace 15 hours and continuous blown with nitrogen gas (sulphonation). This heterogeneous solid acid is used in the both transesterification and esterification to produce FAME. Moreover, in the optimal reaction conditions, this catalyst offers a stable catalytic effect. After 20 times usage in optimal reaction condition, the catalytic activity remains unchanged.

Ancillary ligand-free copper catalysed hydrohydrazination of terminal alkynes with NH2NH2.

Science.gov (United States)

Peltier, Jesse L; Jazzar, Rodolphe; Melaimi, Mohand; Bertrand, Guy

2016-02-14

An efficient and selective Cu-catalysed hydrohydrazination of terminal alkynes with parent hydrazine is reported. The methodology tolerates a broad range of functional groups, allows for the synthesis of symmetrical and unsymmetrical azines, and can be extended to hydrazine derivatives and amines.

Endogenous cytokinin profiles and their relationships to between-family differences during adventitious caulogenesis in Pinus pinea cotyledons

Czech Academy of Sciences Publication Activity Database

Cuesta, C.; Novák, Ondřej; Ordas, R. J.; Fernandez, B.; Strnad, Miroslav; Doležal, Karel; Rodriguez, A.

2012-01-01

Roč. 169, č. 18 (2012), s. 1830-1830-1837 ISSN 0176-1617 R&D Projects: GA AV ČR KAN200380801 Grant - others:GA MŠk(CZ) ED0007/01/01 Program:ED Institutional research plan: CEZ:AV0Z50380511 Keywords : Natural cytokinins * Adventitious shoot organogenesis * Pinus pinea Subject RIV: EC - Immunology Impact factor: 2.699, year: 2012

Beta-lactam degradation catalysed by Cd2+ ion in methanol.

Science.gov (United States)

Martínez, J H; Navarro, P G; Garcia, A A; de las Parras, P J

1999-08-01

Kinetic schemes are established for degradation catalysed by Cd2+ ions in methanolic medium for penicillin G, penicillin V and cephalothin, a cephalosporin. Methanolysis of penicillin V and cephalothin occurs with the formation of a single substrate-metal ion intermediate complex, SM, while degradation of penicillin G occurs with the initial formation of two complexes with different stoichiometry, SM and S2M. In each case. degradation is of first order with respect to SM with rate constant values equal to 0.079 min(-1), 0.120 min(-1) and 0.166 min(-1) at 20, 25 and 30 degrees C, respectively, for penicillin G; 0.061 min(-1) at 20 degrees C for penicillin V; and 2.0 x 10(-3) min(-1) at 20 degrees C for cephalothin. Activation energy for the decomposition process of the SM intermediate for penicillin G was calculated to be about 5.5 x 10(4) J/mol. Equilibrium constant values between SM compound and S2M at 20 degrees C (77.1 l/mol), 25 degrees C (45.3 l/mol) and at 30 degrees C (25.7 l/mol) were also calculated as well as the normal enthalpy of this equilibrium. With respect to the reaction products there is evidence that Cd2+ becomes part of their structure, forming complexes between Cd2+ and the product resulting from antibiotic methanolysis (L). Some characteristics of these complexes are discussed.

Comparative evaluation of atom mapping algorithms for balanced metabolic reactions: application to Recon 3D.

Science.gov (United States)

Preciat Gonzalez, German A; El Assal, Lemmer R P; Noronha, Alberto; Thiele, Ines; Haraldsdóttir, Hulda S; Fleming, Ronan M T

2017-06-14

The mechanism of each chemical reaction in a metabolic network can be represented as a set of atom mappings, each of which relates an atom in a substrate metabolite to an atom of the same element in a product metabolite. Genome-scale metabolic network reconstructions typically represent biochemistry at the level of reaction stoichiometry. However, a more detailed representation at the underlying level of atom mappings opens the possibility for a broader range of biological, biomedical and biotechnological applications than with stoichiometry alone. Complete manual acquisition of atom mapping data for a genome-scale metabolic network is a laborious process. However, many algorithms exist to predict atom mappings. How do their predictions compare to each other and to manually curated atom mappings? For more than four thousand metabolic reactions in the latest human metabolic reconstruction, Recon 3D, we compared the atom mappings predicted by six atom mapping algorithms. We also compared these predictions to those obtained by manual curation of atom mappings for over five hundred reactions distributed among all top level Enzyme Commission number classes. Five of the evaluated algorithms had similarly high prediction accuracy of over 91% when compared to manually curated atom mapped reactions. On average, the accuracy of the prediction was highest for reactions catalysed by oxidoreductases and lowest for reactions catalysed by ligases. In addition to prediction accuracy, the algorithms were evaluated on their accessibility, their advanced features, such as the ability to identify equivalent atoms, and their ability to map hydrogen atoms. In addition to prediction accuracy, we found that software accessibility and advanced features were fundamental to the selection of an atom mapping algorithm in practice.

Réaction du polyisobutène chloré sur l'anhydride maléique : mécanisme. Catalyse par l'anhydride dichloromaléique Reaction of Chlorinated Polyisobutene on Maleic Anhydride. Mechanism. Catalysis by Dichloromaleic Anhydride

Directory of Open Access Journals (Sweden)

Sillion B.

2006-11-01

Full Text Available Dans cet article le mécanisme de la réaction de condensation du polyisobutène chloré sur l'anhydride maléique, qui sert dans la synthèse d'additif pour lubrifiant, est étudié par une cinétique globale et par un travail sur composés modèles. Il est montré que, dans cette réaction, l'anhydride maléique joue un double rôle : de catalyseur de déshydrochloration par une réactivité de type acide de Lewis organique, de réactif comme diénophile. Grâce à ces résultats, il est proposé une catalyse par l'anhydride dichloromaléique, qui permet une amélioration sensible du procédé. This article examines the mechanism of the chlorinated-polyisobutene condensation reaction on maleic anhydride. The overall kinetics and model compounds are investigated for this reaction which is used in the synthesis of lubricant additives. Maleic anhydride is shown to play the dual role of a dehydrochlorination catalyst by having a reactivity of the organic Lewis acid type and of a reactant like dienophile. These results are used to propose a catalysis by dichloromaleic anhydride which appreciably improves the process.

Effect of cytokinins on delaying petunia flower senescence: a transcriptome study approach.

Science.gov (United States)

Trivellini, Alice; Cocetta, Giacomo; Vernieri, Paolo; Mensuali-Sodi, Anna; Ferrante, Antonio

2015-01-01

Flower senescence is a fascinating natural process that represents the final developmental stage in the life of a flower. Plant hormones play an important role in regulating the timing of flower senescence. Ethylene is a trigger and usually accelerates the senescence rate, while cytokinins are known to delay it. The aim of this work was to study the effect of 6-benzylaminopurine (BA) on petal senescence by transcript profile comparison after 3 or 6 h using a cross-species method by hybridizing petunia samples to a 4 × 44 K Agilent tomato array. The relative content of ethylene, abscisic acid, anthocyanins, total carotenoids and total phenols that determine the physiological behaviours of the petal tissue were measured. BA treatment prolonged the flower life and increased the concentrations of phenols and anthocyanins, while total carotenoids did not increase and were lower than the control. The ethylene biosynthetic and perception gene expressions were studied immediately after treatment until 24 h and all genes were repressed, while ethylene production was strongly induced after 4 days. The microarray analyses highlighted that BA strongly affected gene regulation after 3 h, but only 14% of genes remained differentially expressed after 6 h. The most affected pathways and genes were those related to stress, such as heat shock proteins, abscisic acid (ABA) catabolism and its signalling pathway, lipid metabolism and antioxidant defence systems. A gene annotation enrichment analysis using DAVID showed that the most important gene clusters were involved in energy generation and conservation processes. In addition to the ethylene pathway, cytokinins seem to be strongly involved the regulation of the ABA response in flower tissues.

Isopentenyltransferase-1 (IPT1) knockout in Physcomitrella together with phylogenetic analyses of IPTs provide insights into evolution of plant cytokinin biosynthesis

Czech Academy of Sciences Publication Activity Database

Lindner, A.C.; Lang, D.; Seifert, M.; Podlešáková, Kateřina; Novák, Ondřej; Strnad, Miroslav; Reski, R.; von Schwartzenberg, K.

2014-01-01

Roč. 65, č. 9 (2014), s. 2533-2543 ISSN 0022-0957 R&D Projects: GA MŠk(CZ) LO1204 Institutional support: RVO:61389030 Keywords : isopentenyltransferases * isopentenyladenosine * cytokinin Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 5.526, year: 2014

Deciphering the growth pattern and phytohormonal content in Saskatoon berry (Amelanchier alnifolia) in response to in vitro cytokinin application

Czech Academy of Sciences Publication Activity Database

Moyo, M.; Aremu, A.O.; Plačková, Lenka; Plíhalová, Lucie; Pěnčík, Aleš; Novák, Ondřej; Holub, J.; Doležal, Karel; Van Staden, J.

2018-01-01

Roč. 42, MAY 25 (2018), s. 85-94 ISSN 1871-6784 R&D Projects: GA MŠk(CZ) LO1204 Institutional support: RVO:61389030 Keywords : Auxins * Endogenous cytokinins * Micropropagation * Organogenesis * Saskatoon berry * Topolins Subject RIV: EB - Genetics ; Molecular Biology OBOR OECD: Plant sciences, botany Impact factor: 3.813, year: 2016

Computing the correlation between catalyst composition and its performance in the catalysed process

Czech Academy of Sciences Publication Activity Database

Holeňa, Martin; Steinfeldt, N.; Baerns, M.; Štefka, David

2012-01-01

Roč. 43, 10 August (2012), s. 55-67 ISSN 0098-1354 R&D Projects: GA ČR GA201/08/0802 Institutional support: RVO:67985807 Keywords : catalysed process * catalyst performance * correlation measures * estimating correlation value * analysis of variance * regression trees Subject RIV: IN - Informatics, Computer Science Impact factor: 2.091, year: 2012

Effects of Cytokinin and Nitrogen on Drought Tolerance of Creeping Bentgrass.

Directory of Open Access Journals (Sweden)

Zhihui Chang

Full Text Available Cytokinin (CK is a vital plant hormone that controls many aspects of growth and development in plants. Nitrogen (N is the indispensable macronutrient needed in plants and also one of the most important limiting factors for plant growth. This study was designed to investigate the simultaneous effects of CK and N on the visual turf quality and antioxidant metabolism of drought-stressed creeping bentgrass (Agrostis stolonifera L.. 'PennA-4' creeping bentgrass treated with trans-zeatin riboside at three rates of CK concentrations of 0, 10 and 100 μM (designated by CK0, 10, and 100 and two nitrogen rates with 2.5 and 7.5 kg N·ha-1 every 15 days (designated by low and high N in a complete factorial arrangement was grown under two soil moisture regimes: well-watered and drought stress. Exogenous CK improved turf quality and delayed leaf wilting under drought stress, especially under high N. The grasses treated with CK10 and CK100 had lower O2- production and H2O2 concentration than those without CK treatment. The CK100 treatment enhanced the activities of superoxide dismutase (SOD, ascorbate peroxidase (APX, catalase (CAT, and guaiacol peroxidase (POD by 25%, 22%, 17% and 24%, respectively, relative to CK0. Moreover, the activity changes of the antioxidant enzyme isoforms were more significant under high N condition relative to low N condition. Our results demonstrated the beneficial impacts of CK and N on physiological reactions, especially antioxidant metabolism, and foliar application of CK at 10 or 100 μM plus 7.5 kg ha-1 N biweekly may improve drought stress resistance of creeping bentgrass.

Action of sulphite on plant malate dehydrogenase

Energy Technology Data Exchange (ETDEWEB)

Ziegler, I.

1974-01-01

SO/sub 3//sup 2 -/ acts on NAD- and NADP-dependent malate dehydrogenase in several ways. Firstly, SO/sub 3//sup 2 -/ favours the appearance of low MW species (65000 and 39000 daltons) in Sephadex gel chromatography. Secondly, the enzyme from which is obtained by gel chromatography with dithioerythritol plus nucleotide cofactor is changed in the presence of SO/sub 3//sup 2 -/. This is indicated by the appearance of a linear reaction (instead of curvilinear), and by the abolition of the biphasic sigmoidal kinetics on varying substrate and cofactor concentrations. Thus the inhibition of initial velocity at high substrate or cofactor concentrations is even more marked than at lower ones. Thirdly, SO/sub 3//sup 2 -/ strongly reduces the activity in substrate saturating conditions.

Changes in the Chlorophyll Content and Cytokinin Levels in the Top Three Leaves of New Plant Type Rice During Grain Filling

Czech Academy of Sciences Publication Activity Database

Rubia, L.; Rangan, L.; Kamínek, Miroslav; Dobrev, Petre; Malbeck, Jiří; Fowler, M.; Khush, G.; Elliott, M.

2014-01-01

Roč. 33, č. 1 (2014), s. 66-76 ISSN 0721-7595 R&D Projects: GA MŠk 1M06030 Institutional support: RVO:61389030 Keywords : Chlorophyll * Cytokinins * Grain filling Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 2.237, year: 2014

A Phenylurea Cytokinin, CPPU, Elevated Reducing Sugar and Correlated to Andrographolide Contents in Leaves of Andrographis paniculata (Burm. F.) Wall. Ex Nees.

Science.gov (United States)

Worakan, Phapawee; Karaket, Netiya; Maneejantra, Nuchada; Supaibulwatana, Kanyaratt

2017-02-01

Cytokinins are phytohormones that play multiple roles to control plant growth and development. In this study, leaf biomass and the production of andrographolide compounds in a medicinal plant Andrographis paniculata were significantly increased after exogenously treating with the synthetic cytokinin cytokinin-1-(2-chloro-4-pyridyl)-3-phenylurea (CPPU) at 0 (water), 5, or 10 mg L -1 and observed the results for 24 h, 48 h, and 7 days of treatment. It was found that CPPU could significantly enhance new axillary bud formation and further promote branching 4.6-5.6-fold higher, resulting in higher fresh weight (FW) and dry weight (DW) than the control. Application of CPPU at 5 mg L -1 significantly promoted the highest contents of total reducing sugar at 2.5-fold in leaves and at 1.5-fold in roots. Although treatments of CPPU significantly affected the increasing contents of chlorophyll and carotenoid (1.2-1.6-fold), CPPU at 10 mg L -1 slightly caused leaf stress and chlorophyll reduction. Interestingly, 5 mg L -1 CPPU could enhance andrographolide content, an active anti-infectious compound in Andrographis paniculata (2.2-fold higher than the control) that reached the highest content at 24 h after treatment. This study suggested that CPPU should be suitable for field application to promote leaf yields and induce the production of useful pharmaceutical compounds in Andrographis paniculata.

Activation tagging identifies a gene from Petunia hybrids responsible for the production of active cytokinins in plants

Czech Academy of Sciences Publication Activity Database

Zubko, E.; Adams, Ch.; Macháčková, Ivana; Malbeck, Jiří; Scollan, C.; Meyer, P.

2002-01-01

Roč. 29, č. 6 (2002), s. 797-808 ISSN 0960-7412 R&D Projects: GA ČR GA206/00/1354; GA MŠk LN00A081; GA ČR GA206/02/0967; GA ČR GA522/02/0530 Institutional research plan: CEZ:AV0Z5038910 Keywords : cytokinin * isopentenyl transferase * plant hormones Subject RIV: EF - Botanics Impact factor: 5.850, year: 2002

A new approach for cytokinin isolation from Arabidopsis tissues using miniaturized purification: pipette tip solid-phase extraction

Czech Academy of Sciences Publication Activity Database

Svačinová, Jana; Novák, Ondřej; Plačková, Lenka; Lenobel, René; Holík, Josef; Strnad, Miroslav; Doležal, Karel

2012-01-01

Roč. 8, _ (2012), s. 17 ISSN 1746-4811 R&D Projects: GA TA ČR TA01010861; GA AV ČR KAN200380801 Grant - others:GA MŠk(CZ) ED0007/01/01 Program:ED Institutional research plan: CEZ:AV0Z50380511 Keywords : Pipette tip solid-phase extraction (PT-SPE) * Arabidopsis thaliana * Cytokinins Subject RIV: EC - Immunology Impact factor: 2.667, year: 2012

Changes in cinnamyl alcohol dehydrogenase activities from sugarcane cultivars inoculated with Sporisorium scitamineum sporidia.

Science.gov (United States)

Santiago, Rocío; Alarcón, Borja; de Armas, Roberto; Vicente, Carlos; Legaz, María Estrella

2012-06-01

This study describes a method for determining cinnamyl alcohol dehydrogenase activity in sugarcane stems using reverse phase (RP) high-performance liquid chromatography to elucidate their possible lignin origin. Activity is assayed using the reverse mode, the oxidation of hydroxycinnamyl alcohols into hydroxycinnamyl aldehydes. Appearance of the reaction products, coniferaldehyde and sinapaldehyde is determined by measuring absorbance at 340 and 345 nm, respectively. Disappearance of substrates, coniferyl alcohol and sinapyl alcohol is measured at 263 and 273 nm, respectively. Isocratic elution with acetonitrile:acetic acid through an RP Mediterranea sea C18 column is performed. As case examples, we have examined two different cultivars of sugarcane; My 5514 is resistant to smut, whereas B 42231 is susceptible to the pathogen. Inoculation of sugarcane stems elicits lignification and produces significant increases of coniferyl alcohol dehydrogenase (CAD) and sinapyl alcohol dehydrogenase (SAD). Production of lignin increases about 29% in the resistant cultivar and only 13% in the susceptible cultivar after inoculation compared to uninoculated plants. Our results show that the resistance of My 5514 to smut is likely derived, at least in part, to a marked increase of lignin concentration by the activation of CAD and SAD. Copyright © Physiologia Plantarum 2012.

Exogenous Cytokinins Increase Grain Yield of Winter Wheat Cultivars by Improving Stay-Green Characteristics under Heat Stress.

Directory of Open Access Journals (Sweden)

Dongqing Yang

Full Text Available Stay-green, a key trait of wheat, can not only increase the yield of wheat but also its resistance to heat stress during active photosynthesis. Cytokinins are the most potent general coordinator between the stay-green trait and senescence. The objectives of the present study were to identify and assess the effects of cytokinins on the photosynthetic organ and heat resistance in wheat. Two winter wheat cultivars, Wennong 6 (a stay-green cultivar and Jimai 20 (a control cultivar, were subjected to heat stress treatment from 1 to 5 days after anthesis (DAA. The two cultivars were sprayed daily with 10 mg L-1 of 6-benzylaminopurine (6-BA between 1 and 3 DAA under ambient and elevated temperature conditions. We found that the heat stress significantly decreased the number of kernels per spike and the grain yield (P < 0.05. Heat stress also decreased the zeatin riboside (ZR content, but increased the gibberellin (GA3, indole-3-acetic acid (IAA, and abscisic acid (ABA contents at 3 to 15 DAA. Application of 6-BA significantly (P < 0.05 increased the grain-filling rate, endosperm cell division rate, endosperm cell number, and 1,000-grain weight under heated condition. 6-BA application increased ZR and IAA contents at 3 to 28 DAA, but decreased GA3 and ABA contents. The contents of ZR, ABA, and IAA in kernels were positively and significantly correlated with the grain-filling rate (P < 0.05, whereas GA3 was counter-productive at 3 to 15 DAA. These results suggest that the decrease in grain yield under heat stress was due to a lower ZR content and a higher GA3 content compared to that at elevated temperature during the early development of the kernels, which resulted in less kernel number and lower grain-filling rate. The results also provide essential information for further utilization of the cytokinin substances in the cultivation of heat-resistant wheat.

Effects of cytokinins on antioxidant enzymes in in vitro grown shoots of Pelargonium hortorum L. H. Bayley

Directory of Open Access Journals (Sweden)

Agnieszka Wojtania

2014-12-01

Full Text Available The aim of this study was to determine the influence of meta-topolin (mT and 6-benzyl-aminopurine (BAP on the hydrogen peroxide (H2O2 level and antioxidant enzymes activities in relation to the shoot formation and senescence process in Pelargonium hortorum cultivars, which differ in their susceptibility to leaf yellowing under in vitro conditions. In an early senescing cultivar ‘Grand Prix’, the addition of an aromatic cytokinin mT to abscisic acid (ABA-enriched Murashige and Skoog (MS basal medium more efficiently inhibited leaf yellowing than BAP. In both genotypes, meta-topolin was also the most effective in shoot formation. It was found that Pelargonium species varying in their susceptibility to senescence differ in H2O2 production and antioxidant enzymes activities. Generally, meta-topolin more effectively enhanced H2O2 production and POD activity than BAP and control medium, but its effect depended on genotype. The highest H2O2 production stimulated by mT was observed on day 5 of subculture in late senescing cv. ‘Bergpalais’. In both geranium genotypes, superoxide dismutase (SOD and catalase (CAT levels were highest at the beginning of the subculture period, during the initiation of shoot formation. SOD showed the highest activity on day 5 of subculture on the medium without cytokinin and generally being higher in cv. ‘Bergpalais’ than in cv. ‘Grand Prix’. CAT activity was positively regulated by both cytokinins. POD activity was most effectively enhanced by mT, but on different days of subculture - on the 2nd day of subculture in cv. ‘Bergpalais’ and on the 22nd day of subculture in cv. ‘Grand Prix’. The enhanced activity of POD in the presence of mT, 4-fold higher than on control medium, at the end of subculture in P. hortorum ‘Grand Prix’ coincided with the inhibition of leaf senescence.

Metabolite responses to exogenous application of nitrogen, cytokinin, and ethylene inhibitors in relation to heat-induced senescence in creeping bentgrass.

Directory of Open Access Journals (Sweden)

David Jespersen

Full Text Available The exogenous application of ethylene inhibitors, cytokinins, or nitrogen has previously been shown to suppress heat-induced senescence and improve heat tolerance in cool-season grasses. The objectives of this study were to examine metabolic profiles altered by exogenous treatment of creeping bentgrass with an ethylene inhibitor, cytokinin or nitrogen under heat stress and to determine metabolic pathways regulated by those compounds in association with their effectiveness for improving heat tolerance. Creeping bentgrass (Agostis stolonifera plants (cv. Penncross were foliar sprayed with 18 mM carbonyldiamide (N source, 25 μM aminoethoxyvinylglycine (AVG, ethylene inhibitor, 25 μM zeatin riboside (ZR, cytokinin, or a water control, and then exposed to 20/15°C (day/night or 35/30°C (heat stress in growth chambers. All three exogenous treatments suppressed leaf senescence, as manifested by increased turf quality and chlorophyll content, and reduced electrolyte leakage under heat stress. Polar metabolite profiling identified increases in the content of certain organic acids (i.e. citric and malic acid, sugar alcohols, disaccharides (sucrose, and decreased accumulations of monosaccharides (i.e. glucose and fructose with exogenous treatment of N, AVG, or ZR at the previously mentioned concentrations when compared to the untreated control under heat stress. Nitrogen stimulated amino acid accumulation whereas AVG and ZR reduced amino acid accumulation compared to the untreated control under heat stress. These results revealed that the alleviation of heat-induced leaf senescence by N, AVG, and ZR could be due to changes in the accumulation of metabolites involved in osmoregulation, antioxidant metabolism, carbon and nitrogen metabolism, as well as stress signaling molecules.

Click synthesis of 1,4-disubstituted-1,2,3-triazoles catalysed by CuO ...

Indian Academy of Sciences (India)

Click synthesis of 1,4-disubstituted-1,2,3-triazoles catalysed by. CuO–CeO2 nanocomposite in the presence of amberlite-supported azide. JALAL ALBADIa,∗, JAFAR ABBASI SHIRANb and AZAM MANSOURNEZHADc. aBehbahan Khatam Alanbia University of Technology, Behbahan 6361647189, Iran. bFaculty of Science ...

Benzyladenine-induced inhibition of flowering in Chenopodium rubrum in vitro is not related to the levels of isoprenoid cytokinins

Czech Academy of Sciences Publication Activity Database

Blažková, Alena; Macháčková, Ivana; Eder, Josef; Krekule, Jan

2001-01-01

Roč. 34, č. 2 (2001), s. 159-166 ISSN 0167-6903 R&D Projects: GA ČR GV206/96/K188; GA ČR GA206/00/1354 Institutional research plan: CEZ:AV0Z5038910 Keywords : benzylaminopurine * Chenopodium rubrum * cytokinins Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 0.761, year: 2001

cis-Chlorobenzene Dihydrodiol Dehydrogenase (TcbB) from Pseudomonas sp. Strain P51, Expressed in Escherichia coli DH5α(pTCB149), Catalyzes Enantioselective Dehydrogenase Reactions

OpenAIRE

Raschke, Henning; Fleischmann, Thomas; Van Der Meer, Jan Roelof; Kohler, Hans-Peter E.

1999-01-01

cis-Chlorobenzene dihydrodiol dehydrogenase (CDD) from Pseudomonas sp. strain P51, cloned into Escherichia coli DH5α(pTCB149) was able to oxidize cis-dihydrodihydroxy derivatives (cis-dihydrodiols) of dihydronaphthalene, indene, and four para-substituted toluenes to the corresponding catechols. During the incubation of a nonracemic mixture of cis-1,2-indandiol, only the (+)-cis-(1R,2S) enantiomer was oxidized; the (−)-cis-(S,2R) enantiomer remained unchanged. CDD oxidized both enantiomers of ...

Functional roles of three cutin biosynthetic acyltransferases in cytokinin responses and skotomorphogenesis.

Directory of Open Access Journals (Sweden)

Lei Wu

Full Text Available Cytokinins (CKs regulate plant development and growth via a two-component signaling pathway. By forward genetic screening, we isolated an Arabidopsis mutant named grow fast on cytokinins 1 (gfc1, whose seedlings grew larger aerial parts on MS medium with CK. gfc1 is allelic to a previously reported cutin mutant defective in cuticular ridges (dcr. GFC1/DCR encodes a soluble BAHD acyltransferase (a name based on the first four enzymes characterized in this family: Benzylalcohol O-acetyltransferase, Anthocyanin O-hydroxycinnamoyltransferase, anthranilate N-hydroxycinnamoyl/benzoyltransferase and Deacetylvindoline 4-O-acetyltransferase with diacylglycerol acyltransferase (DGAT activity in vitro and is necessary for normal cuticle formation on epidermis in vivo. Here we show that gfc1 was a CK-insensitive mutant, as revealed by its low regeneration frequency in vitro and resistance to CK in adventitious root formation and dark-grown hypocotyl inhibition assays. In addition, gfc1 had de-etiolated phenotypes in darkness and was therefore defective in skotomorphogenesis. The background expression levels of most type-A Arabidopsis Response Regulator (ARR genes were higher in the gfc1 mutant. The gfc1-associated phenotypes were also observed in the cutin-deficient glycerol-3-phosphate acyltransferase 4/8 (gpat4/8 double mutant [defective in glycerol-3-phosphate (G3P acyltransferase enzymes GPAT4 and GPAT8, which redundantly catalyze the acylation of G3P by hydroxyl fatty acid (OH-FA], but not in the cutin-deficient mutant cytochrome p450, family 86, subfamily A, polypeptide 2/aberrant induction of type three 1 (cyp86A2/att1, which affects the biosynthesis of some OH-FAs. Our results indicate that some acyltransferases associated with cutin formation are involved in CK responses and skotomorphogenesis in Arabidopsis.

Ag-catalysed cutting of multi-walled carbon nanotubes

International Nuclear Information System (INIS)

La Torre, A; Rance, G A; Miners, S A; Lucas, C Herreros; Smith, E F; Giménez-López, M C; Khlobystov, A N; Fay, M W; Brown, P D; Zoberbier, T; Kaiser, U

2016-01-01

In this work, the cutting of carbon nanotubes is investigated using silver nanoparticles deposited on arc discharge multi-walled carbon nanotubes. The composite is subsequently heated in air to fabricate shortened multi-walled nanotubes. Complementary transmission electron microscopy and spectroscopy techniques shed light on the cutting mechanism. The nanotube cutting is catalysed by the fundamental mechanism based on the coordination of the silver atoms to the π-bonds of carbon nanotubes. As a result of the metal coordination, the strength of the carbon–carbon bond is reduced, promoting the oxidation of carbon at lower temperature when heated in air, or lowering the activation energy required for the removal of carbon atoms by electron beam irradiation, assuring in both cases the cutting of the nanotubes. (paper)

Deracemization of Secondary Alcohols by using a Single Alcohol Dehydrogenase

KAUST Repository

Karume, Ibrahim

2016-03-01

© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. We developed a single-enzyme-mediated two-step approach for deracemization of secondary alcohols. A single mutant of Thermoanaerobacter ethanolicus secondary alcohol dehydrogenase enables the nonstereoselective oxidation of racemic alcohols to ketones, followed by a stereoselective reduction process. Varying the amounts of acetone and 2-propanol cosubstrates controls the stereoselectivities of the consecutive oxidation and reduction reactions, respectively. We used one enzyme to accomplish the deracemization of secondary alcohols with up to >99% ee and >99.5% recovery in one pot and without the need to isolate the prochiral ketone intermediate.

CYTOKININ OXIDASE/DEHYDROGENASE3 Maintains Cytokinin Homeostasis during Root and Nodule Development in Lotus japonicus

Czech Academy of Sciences Publication Activity Database

Reid, D.E.; Heckmann, A.B.; Novák, Ondřej; Kelly, S.; Stougaard, J.

2016-01-01

Roč. 170, č. 2 (2016), s. 1060-1074 ISSN 0032-0889 R&D Projects: GA MŠk LK21306 Institutional support: RVO:61389030 Keywords : DEPENDENT PROTEIN-KINASE * NODULATION SIGNALING PATHWAY * SYMBIOTIC ORGAN DEVELOPMENT Subject RIV: EF - Botanics Impact factor: 6.456, year: 2016

High Performance Liquid Chromatography/Electrochemistry/High Resolution Electrospray Ionization-Mass Spectrometry (HPLC/EC/HR ESI-MS) Characterization of Selected Cytokinins Oxidation Products

Czech Academy of Sciences Publication Activity Database

Karady, Michal; Novák, Ondřej; Horna, A.; Strnad, Miroslav; Doležal, Karel

2015-01-01

Roč. 27, č. 2 (2015), s. 406-414 ISSN 1040-0397 R&D Projects: GA MŠk(CZ) LO1204 Institutional support: RVO:61389030 Keywords : Electrochemistry * Cytokinin * Oxidative metabolism Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 2.471, year: 2015

Asymmetric Reduction of Substituted 2-Tetralones by Thermoanaerobacter pseudoethanolicus Secondary Alcohol Dehydrogenase

KAUST Repository

Bsharat, Odey; Musa, Musa M.; Vieille, Claire; Oladepo, Sulayman; Takahashi, Masateru; Hamdan, Samir

2017-01-01

Ketones bearing two bulky substituents, named bulky-bulky ketones, were successfully reduced to their corresponding optically enriched alcohols by using various mutants of Thermoanaerobacter pseudoethanolicus secondary alcohol dehydrogenase (TeSADH). Substituted 2-tetralones, in particular, were reduced to 2-tetralols with high conversion and high enantioselectivity. The pharmacological importance of substituted 2-tetralols as key drug-building blocks makes our biocatalytic reduction method a highly essential tool. We showed that changing the position of the substituent on the aromatic ring of 2-tetralones impacts their binding affinity and the reaction maximum catalytic rate. Docking studies with several TeSADH mutants explain how the position of the substituent on the tetralone influences the binding orientation of substituted 2-tetralones and their reaction stereoselectivity.

Asymmetric Reduction of Substituted 2-Tetralones by Thermoanaerobacter pseudoethanolicus Secondary Alcohol Dehydrogenase

KAUST Repository

Bsharat, Odey

2017-01-30

Ketones bearing two bulky substituents, named bulky-bulky ketones, were successfully reduced to their corresponding optically enriched alcohols by using various mutants of Thermoanaerobacter pseudoethanolicus secondary alcohol dehydrogenase (TeSADH). Substituted 2-tetralones, in particular, were reduced to 2-tetralols with high conversion and high enantioselectivity. The pharmacological importance of substituted 2-tetralols as key drug-building blocks makes our biocatalytic reduction method a highly essential tool. We showed that changing the position of the substituent on the aromatic ring of 2-tetralones impacts their binding affinity and the reaction maximum catalytic rate. Docking studies with several TeSADH mutants explain how the position of the substituent on the tetralone influences the binding orientation of substituted 2-tetralones and their reaction stereoselectivity.

Endogenous cytokinins, auxins and abscisic acid in Ulva fasciata (Chlorophyta) and Dictyota humifusa (Phaeophyta): towards understanding their biosynthesis and homoeostasis

Czech Academy of Sciences Publication Activity Database

Stirk, W.A.; Novák, Ondřej; Hradecká, Veronika; Pěnčík, Aleš; Rolčík, Jakub; Strnad, Miroslav; van Staden, J.

2009-01-01

Roč. 44, č. 2 (2009), s. 231-240 ISSN 0967-0262 R&D Projects: GA ČR GA206/05/0894 Institutional research plan: CEZ:AV0Z50380511 Keywords : abscisic acid * auxins * cytokinins Subject RIV: BO - Biophysics Impact factor: 1.556, year: 2009 www.informaworld.com/smpp/content~content=a911046981

Characterization of cDNAs encoding human pyruvate dehydrogenase α subunit

International Nuclear Information System (INIS)

Ho, Lap; Wexler, I.D.; Liu, Techung; Thekkumkara, T.J.; Patel, M.S.

1989-01-01

A cDNA clone (1,423 base pairs) comprising the entire coding region of the precursor form of the α subunit of pyruvate dehydrogenase (E 1 α) has been isolated from a human liver cDNA library in phage λgt11. The first 29 amino acids deduced from the open reading frame correspond to a typical mitochondrial targeting leader sequence. The remaining 361 amino acids, starting at the N terminus with phenylalanine, represent the mature mitochondrial E 1 α peptide. The cDNA has 43 base pairs in the 5' untranslated region and 210 base pairs in the 3' untranslated region, including a polyadenylylation signal and a short poly(A) tract. The nucleotide sequence of human liver E 1 α cDNA was confirmed by the nucleotide sequences of three overlapping fragments generated from human liver and fibroblast RNA by reverse transcription and DNA amplification by the polymerase chain reaction. This consensus nucleotide sequence of human liver E 1 α cDNA resolves existing discrepancies among three previously reported human E 1 α cDNAs and provides the unambiguous reference sequence needed for the characterization of genetic mutations in pyruvate dehydrogenase-deficient patients

Cytokinin Regulation of Gene Expression in the AHP Gene Family in Arabidopsis thaliana

Czech Academy of Sciences Publication Activity Database

Hradilová, Jana; Malbeck, Jiří; Brzobohatý, Břetislav

2007-01-01

Roč. 26, č. 3 (2007), s. 229-244 ISSN 0721-7595 R&D Projects: GA MŠk LN00A081; GA MŠk 1M06030; GA MŠk(CZ) LC06034; GA AV ČR(CZ) IAA600380507; GA AV ČR IAA600040612 Institutional research plan: CEZ:AV0Z50380511; CEZ:AV0Z50040702 Source of funding: V - iné verejné zdroje ; V - iné verejné zdroje ; V - iné verejné zdroje ; V - iné verejné zdroje Keywords : gene expression * AHP gene family * cytokinin signal transduction Subject RIV: EF - Botanics Impact factor: 2.220, year: 2007

The mvp2 mutation affects the generative transition through the modification of transcriptome pattern, salicylic acid and cytokinin metabolism in Triticum monococcum

Czech Academy of Sciences Publication Activity Database

Boldizsár, A.; Vaňková, Radomíra; Novák, A.; Kalapos, S.; Gulyás, Z.; Pál, M.; Floková, Kristýna; Janda, T.; Galiba, G.; Kocsy, G.

2016-01-01

Roč. 202, SEP 1 (2016), s. 21-33 ISSN 0176-1617 R&D Projects: GA MŠk(CZ) LO1204 Institutional support: RVO:61389030 Keywords : Cytokinin * mvp2 mutation * Triticum monococcum Subject RIV: EB - Genetics ; Molecular Biology Impact factor: 3.121, year: 2016

Enzyme catalysed production of sialylated human milk oligosaccharides and galactooligosaccharides by Trypanosoma cruzi trans-sialidase

DEFF Research Database (Denmark)

Holck, Jesper; Larsen, Dorte Møller; Michalak, Malwina

2014-01-01

Bifidobacterium strains in single culture fermentations. The trans-sialidase also catalysed the transfer of sialic acid from CGMP to galacto-oligosaccharides (GOS) and to the human milk oligosaccharide (HMO) backbone lacto-N-tetraose (LNT) to produce 3′-sialyl-GOS, including doubly sialylated GOS products, and 3...

Calcium inhibition of the NAD+-linked isocitrate dehydrogenase from blowfly flight muscle mitochondria.

Science.gov (United States)

Bulos, B A; Thomas, B J; Sacktor, B

1984-08-25

Free Ca2+ was shown to inhibit the NAD+-isocitrate dehydrogenase from blowfly flight muscle mitochondria. Inhibition by free Ca2+ concentrations of 40 microM or greater was found in the absence or presence of ADP and citrate, two known activators of the enzyme. Calcium decreased the affinity of the enzyme for its substrate, the magnesium DL-isocitrate chelate; no change in the apparent V of the reaction was observed. Calcium was inhibitory when activity was measured in the presence of fixed concentrations of magnesium DL-isocitrate chelate in the presence of several fixed concentrations of either free isocitrate3-, an activator, or free Mg2+, an inhibitor of the enzyme. That NAD+-isocitrate dehydrogenase from blowfly flight muscle mitochondria was not activated by micromolar free Ca2+ is consistent with the view that calcium does not play a role in regulating the flux through the tricarboxylate cycle in this species.

Kinetic isotope effect studies on milk xanthine oxidase and on chicken liver xanthine dehydrogenase

International Nuclear Information System (INIS)

D'Ardenne, S.C.; Edmondson, D.E.

1990-01-01

The effect of isotopic substitution of the 8-H of xanthine (with 2 H and 3 H) on the rate of oxidation by bovine xanthine oxidase and by chicken xanthine dehydrogenase has been measured. V/K isotope effects were determined from competition experiments. No difference in H/T (V/K) values was observed between xanthine oxidase and xanthine dehydrogenase. Xanthine dehydrogenase exhibited a larger T/D (V/K) value than that observed for xanthine oxidase. Observed H/T (V/K) values for either enzyme are less than those H/T (V/K) values calculated with D/T (V/K) data. These discrepancies are suggested to arise from the presence of a rate-limiting step(s) prior to the irreversible C-H bond cleavage step in the mechanistic pathways of both enzymes. These kinetic complexities preclude examination of whether tunneling contributes to the reaction coordinate for the H-transfer step in each enzyme. No observable exchange of tritium with solvent is observed during the anaerobic incubation of [8- 3 H]xanthine with either enzyme, which suggests the reverse commitment to catalysis (C r ) is essentially zero. With the assumption of adherence to reduced mass relationships, the intrinsic deuterium isotope effect ( D k) for xanthine oxidation is calculated. By the use of these values and steady-state kinetic data, the minimal rate for the hydrogen-transfer step is calculated to be ∼75-fold faster than k cat for xanthine oxidase and ∼10-fold faster than k cat for xanthine dehydrogenase. Values calculated for each enzyme were found to be identical within experimental uncertainty

Biochemical fate of N6 substituted purines (cytokinins) in normal ripening and mutant tomatoes

International Nuclear Information System (INIS)

Long, A.R.

1987-01-01

The initial rates of disappearance of cytokinins, as determined by high pressure liquid chromatography, for tomatoes which were vacuum infused with benzyladenine and isopentenyladenine were dissimilar between the normal ripening (Ohio CR-6 and Rutgers), ripening inhibited mutant (RIN) and non-ripening mutant (NOR) tomato varieties. Radiolabeled [8- 14 C]Benzyladenine metabolism was followed during a 2 h period utilizing thin layer chromatography and visualization by fluorography. The [8- 14 C]Benzyladenine metabolite patterns were different among the varieties. The [8- 14 C]Benzyladenine metabolite pattern in Ohio CR-6 tomato changed as the fruit ripened

Polymerase chain reaction amplification and cloning of immunogenic protein NAD-dependent beta hydroxybutyryl CoA dehydrogenase gene of Clostridium chauvoei

Directory of Open Access Journals (Sweden)

Saroj K. Dangi

2014-10-01

Full Text Available Aim: The present study was aimed at polymerase chain reaction (PCR amplification and cloning of NAD-dependent betahydroxybutyryl coenzyme A dehydrogenase (BHBD gene of Clostridium chauvoei. Materials and Methods: C. chauvoei was cultured and confirmed by 16-23S rDNA spacer region primers. The primers for nad-bhbd gene of C. chauvoei were designed to aid in cloning into pRham-N-His SUMO-Kan vector, and nad-bhbd gene was amplified by PCR. The amplified nad-bhbd gene was purified and cloned into pRham-N-His SUMO-Kan expression vector. The recombinant plasmid was transformed into E. cloni 10 G cells and the clone was confirmed by colony PCR using the pRham-SUMO-NAD-For and pRham-SUMO-NAD-Rev primers and also by sequencing. Results: PCR amplification of nad-bhbd gene yielded a product length of 844 base pairs which was cloned into pRham-NHis SUMO-Kan vector followed by transformation into E. cloni 10G chemically competent cells. The recombinant clones were characterized by colony PCR, sequencing, followed by basic local alignment search tool (BLAST analysis to confirm the insert. Conclusions: Immunogenic protein NAD- dependent BHBD of C. chauvoei was cloned and the recombinant clones were confirmed by colony PCR and sequencing analysis.

Roles of Proteome Dynamics and Cytokinin Signaling in Root to Hypocotyl Ratio Changes Induced by Shading Roots of Arabidopsis Seedlings

Czech Academy of Sciences Publication Activity Database

Novak, J.; Černý, M.; Pavlů, J.; Zemánková, J.; Skalák, J.; Plačková, Lenka; Brzobohatý, Břetislav

2015-01-01

Roč. 56, č. 5 (2015), s. 1006-1018 ISSN 0032-0781 R&D Projects: GA MŠk(CZ) LO1204 Grant - others:GA ČR(CZ) GAP305/12/2144 Institutional support: RVO:68081707 ; RVO:61389030 Keywords : Arabidopsis thaliana * Cytokinin * Hypocotyl elongation Subject RIV: BO - Biophysics; EF - Botanics (UEB-Q) Impact factor: 4.319, year: 2015

A general strategy for synthesis of cyclophane-braced peptide macrocycles via palladium-catalysed intramolecular sp3 C-H arylation

Science.gov (United States)

Zhang, Xuekai; Lu, Gang; Sun, Meng; Mahankali, Madhu; Ma, Yanfei; Zhang, Mingming; Hua, Wangde; Hu, Yuting; Wang, Qingbing; Chen, Jinghuo; He, Gang; Qi, Xiangbing; Shen, Weijun; Liu, Peng; Chen, Gong

2018-05-01

New methods capable of effecting cyclization, and forming novel three-dimensional structures while maintaining favourable physicochemical properties are needed to facilitate the development of cyclic peptide-based drugs that can engage challenging biological targets, such as protein-protein interactions. Here, we report a highly efficient and generally applicable strategy for constructing new types of peptide macrocycles using palladium-catalysed intramolecular C(sp3)-H arylation reactions. Easily accessible linear peptide precursors of simple and versatile design can be selectively cyclized at the side chains of either aromatic or modified non-aromatic amino acid units to form various cyclophane-braced peptide cycles. This strategy provides a powerful tool to address the long-standing challenge of size- and composition-dependence in peptide macrocyclization, and generates novel peptide macrocycles with uniquely buttressed backbones and distinct loop-type three-dimensional structures. Preliminary cell proliferation screening of the pilot library revealed a potent lead compound with selective cytotoxicity toward proliferative Myc-dependent cancer cell lines.

A comparative study between chemical and enzymatic transesterification of high free fatty acid contained rubber seed oil for biodiesel production

Directory of Open Access Journals (Sweden)

Jilse Sebastian

2016-12-01

Full Text Available The choice of a paramount method for biodiesel production has significance as the demand of alternative fuels like biodiesel is growing rapidly. In the present study, experimental results from chemical-catalysed as well as enzyme-catalysed methods were compared using common influencing parameters such as oil/alcohol molar ratio, catalyst concentration and reaction duration. Requirement of certain solvents to enhance the reaction rate was explained in the enzyme-catalysed transesterification reaction. Biodiesel conversion of more than 90% was attained for chemical-catalysed transesterification, whereas the conversion rate was 85% for enzyme-catalysed method. This gives the indication of further refinement in the enzyme-catalysed transesterification process. The influencing parameters and absolute results of the analysis give the impression of superiority of enzymatic transesterification method for biodiesel production from high free fatty acid-contained rubber seed oil.

In vitro shoot organogenesis and comparative analysis of endogenous phytohormones in kohlrabi (Brassica oleracea var. gongylodes): effects of genotype, explant type and applied cytokinins

Czech Academy of Sciences Publication Activity Database

Cosić, T.; Motyka, Václav; Raspor, M.; Savić, J.; Cingel, A.; Vinterhalter, B.; Vinterhalter, D.; Trávníčková, Alena; Dobrev, Petre; Bohanec, B.; Ninković, S.

2015-01-01

Roč. 121, č. 3 (2015), s. 741-760 ISSN 0167-6857 R&D Projects: GA ČR(CZ) GAP506/11/0774 Institutional support: RVO:61389030 Keywords : Kohlrabi * Cytokinin * Auxin Subject RIV: EF - Botanics Impact factor: 2.390, year: 2015

Reversible inactivation of CO dehydrogenase with thiol compounds

Energy Technology Data Exchange (ETDEWEB)

Kreß, Oliver [Department of Microbiology, University of Bayreuth, 95440 Bayreuth (Germany); Gnida, Manuel [Department of Chemistry, University of Paderborn, 33098 Paderborn (Germany); Pelzmann, Astrid M. [Department of Microbiology, University of Bayreuth, 95440 Bayreuth (Germany); Marx, Christian [Institute of Biochemistry and Biophysics, Friedrich-Schiller-University of Jena, 07745 Jena (Germany); Meyer-Klaucke, Wolfram [Department of Chemistry, University of Paderborn, 33098 Paderborn (Germany); Meyer, Ortwin, E-mail: Ortwin.Meyer@uni-bayreuth.de [Department of Microbiology, University of Bayreuth, 95440 Bayreuth (Germany)

2014-05-09

Highlights: • Rather large thiols (e.g. coenzyme A) can reach the active site of CO dehydrogenase. • CO- and H{sub 2}-oxidizing activity of CO dehydrogenase is inhibited by thiols. • Inhibition by thiols was reversed by CO or upon lowering the thiol concentration. • Thiols coordinate the Cu ion in the [CuSMo(=O)OH] active site as a third ligand. - Abstract: Carbon monoxide dehydrogenase (CO dehydrogenase) from Oligotropha carboxidovorans is a structurally characterized member of the molybdenum hydroxylase enzyme family. It catalyzes the oxidation of CO (CO + H{sub 2}O → CO{sub 2} + 2e{sup −} + 2H{sup +}) which proceeds at a unique [CuSMo(=O)OH] metal cluster. Because of changing activities of CO dehydrogenase, particularly in subcellular fractions, we speculated whether the enzyme would be subject to regulation by thiols (RSH). Here we establish inhibition of CO dehydrogenase by thiols and report the corresponding K{sub i}-values (mM): L-cysteine (5.2), D-cysteine (9.7), N-acetyl-L-cysteine (8.2), D,L-homocysteine (25.8), L-cysteine–glycine (2.0), dithiothreitol (4.1), coenzyme A (8.3), and 2-mercaptoethanol (9.3). Inhibition of the enzyme was reversed by CO or upon lowering the thiol concentration. Electron paramagnetic resonance spectroscopy (EPR) and X-ray absorption spectroscopy (XAS) of thiol-inhibited CO dehydrogenase revealed a bimetallic site in which the RSH coordinates to the Cu-ion as a third ligand ([Mo{sup VI}(=O)OH{sub (2)}SCu{sup I}(SR)S-Cys]) leaving the redox state of the Cu(I) and the Mo(VI) unchanged. Collectively, our findings establish a regulation of CO dehydrogenase activity by thiols in vitro. They also corroborate the hypothesis that CO interacts with the Cu-ion first. The result that thiol compounds much larger than CO can freely travel through the substrate channel leading to the bimetallic cluster challenges previous concepts involving chaperone function and is of importance for an understanding how the sulfuration step in

Oxovanadium(IV)-catalysed oxidation of dibenzothiophene and 4,6-dimethyldibenzothiophene.

Science.gov (United States)

Ogunlaja, Adeniyi S; Chidawanyika, Wadzanai; Antunes, Edith; Fernandes, Manuel A; Nyokong, Tebello; Torto, Nelson; Tshentu, Zenixole R

2012-12-07

The reaction between [V(IV)OSO(4)] and the tetradentate N(2)O(2)-donor Schiff base ligand, N,N-bis(o-hydroxybenzaldehyde)phenylenediamine (sal-HBPD), obtained by the condensation of salicylaldehyde and o-phenylenediamine in a molar ratio of 2 : 1 respectively, resulted in the formation of [V(IV)O(sal-HBPD)]. The molecular structure of [V(IV)O(sal-HBPD)] was determined by single crystal X-ray diffraction, and confirmed the distorted square pyramidal geometry of the complex with the N(2)O(2) binding mode of the tetradentate ligand. The formation of the polymer-supported p[V(IV)O(sal-AHBPD)] proceeded via the nitrosation of sal-HBPD, followed by the reduction with hydrogen to form an amine group that was then linked to Merrifield beads followed by the reaction with [V(IV)OSO(4)]. XPS and EPR were used to confirm the presence of oxovanadium(IV) within the beads. The BET surface area and porosity of the heterogeneous catalyst p[V(IV)O(sal-AHBPD)] were found to be 6.9 m(2) g(-1) and 180.8 Å respectively. Microanalysis, TG, UV-Vis and FT-IR were used for further characterization of both [V(IV)O(sal-HBPD)] and p[V(IV)O(sal-AHBPD)]. Oxidation of dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) was investigated using [V(IV)O(sal-HBPD)] and p[V(IV)O(sal-AHBPD)] as catalysts. Progress for oxidation of these model compounds was monitored with a gas chromatograph fitted with a flame ionization detector. The oxidation products were characterized using gas chromatography-mass spectrometry, microanalysis and NMR. Dibenzothiophene sulfone (DBTO(2)) and 4,6-dimethyldibenzothiophene sulfone (4,6-DMDBTO(2)) were found to be the main products of oxidation. Oxovanadium(IV) Schiff base microspherical beads, p[V(IV)O(sal-AHBPD)], were able to catalyse the oxidation of sulfur in dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DMDBT) to a tune of 88.0% and 71.8% respectively after 3 h at 40 °C. These oxidation results show promise for potential application

Reaction kinetics of bond rotations in graphene

KAUST Repository

Skowron, Stephen T.; Koroteev, Victor O.; Baldoni, Matteo; Lopatin, Sergei; Zurutuza, Amaia; Chuvilin, Andrey; Besley, Elena

2016-01-01

The formation and healing processes of the fundamental topological defect in graphitic materials, the Stone-Wales (SW) defect, are brought into a chemical context by considering the rotation of a carbon-carbon bond as chemical reaction. We investigate the rates and mechanisms of these SW transformations in graphene at the atomic scale using transmission electron microscopy. We develop a statistical atomic kinetics formalism, using direct observations obtained under different conditions to determine key kinetic parameters of the reactions. Based on the obtained statistics we quantify thermally and irradiation induced routes, identifying a thermal process of healing with an activation energy consistent with predicted adatom catalysed mechanisms. We discover exceptionally high rates for irradiation induced SW healing, incompatible with the previously assumed mechanism of direct knock-on damage and indicating the presence of an efficient nonadiabatic coupling healing mechanism involving beam induced electronic excitations of the SW defect.

Reaction kinetics of bond rotations in graphene

KAUST Repository

Skowron, Stephen T.

2016-04-12

The formation and healing processes of the fundamental topological defect in graphitic materials, the Stone-Wales (SW) defect, are brought into a chemical context by considering the rotation of a carbon-carbon bond as chemical reaction. We investigate the rates and mechanisms of these SW transformations in graphene at the atomic scale using transmission electron microscopy. We develop a statistical atomic kinetics formalism, using direct observations obtained under different conditions to determine key kinetic parameters of the reactions. Based on the obtained statistics we quantify thermally and irradiation induced routes, identifying a thermal process of healing with an activation energy consistent with predicted adatom catalysed mechanisms. We discover exceptionally high rates for irradiation induced SW healing, incompatible with the previously assumed mechanism of direct knock-on damage and indicating the presence of an efficient nonadiabatic coupling healing mechanism involving beam induced electronic excitations of the SW defect.

Occurrence of nutrients and plant hormones (cytokinins and IAA) in the water fern Salvinia molesta during growth and composting

Czech Academy of Sciences Publication Activity Database

Arthur, G. D.; Stirk, W. A.; Novák, Ondřej; Hekera, P.; van Staden, J.

2007-01-01

Roč. 61, č. 2 (2007), s. 137-144 ISSN 0098-8472 R&D Projects: GA MŠk(CZ) LC06034; GA ČR GA206/05/0894 Institutional research plan: CEZ:AV0Z50380511 Source of funding: V - iné verejné zdroje ; V - iné verejné zdroje Keywords : auxins * culture medium * cytokinins Subject RIV: BO - Biophysics Impact factor: 1.810, year: 2007

Hydrolysis reaction of 2,4-dichlorophenoxyacetic acid. A kinetic and computational study

Science.gov (United States)

Romero, Jorge Marcelo; Jorge, Nelly Lidia; Grand, André; Hernández-Laguna, Alfonso

2015-10-01

The degradation of the 2,4-dichlorophenoxyacetic acid in aqueous solution is an hydrolysis reaction. Two products are identified: 2,4-dichlorophenol and glycolic acid. Reaction is investigated as a function of pH and temperature, and it is first-order kinetics and pH-dependent. Reaction is modeled in gas phase, where a proton catalyses the reaction. Critical points of PES are calculated at B3LYP/6-311++G(3df,2p), and aug-cc-pvqz//6-311++G(3df,2p) levels plus ZPE at 6-311++G(3df,2p) level. The activation barrier is 21.2 kcal/mol. Theoretical results agree with the experimental results. A second mechanism related with a Cl2Phsbnd Osbnd CH2sbnd COOH⋯H2O complex is found, but with a rate limiting step of 38.4 kcal/mol.

Genes co-regulated with LBD16 in nematode feeding sites inferred from in silico analysis show similarities to regulatory circuits mediated by the auxin/cytokinin balance in Arabidopsis.

Science.gov (United States)

Cabrera, Javier; Fenoll, Carmen; Escobar, Carolina

2015-01-01

Plant endoparasitic nematodes, root-knot and cyst nematodes (RKNs and CNs) induce within the root vascular cylinder transfer cells used for nourishing, termed giant cells (GCs) and syncytia. Understanding the molecular mechanisms behind this process is essential to develop tools for nematode control. Based on the crucial role in gall development of LBD16, also a key component of the auxin pathway leading to the divisions in the xylem pole pericycle during lateral root (LR) formation, we investigated genes co-regulated with LBD16 in different transcriptomes and analyzed their similarities and differences with those of RKNs and CNs feeding sites (FS). This analysis confirmed LBD16 and its co-regulated genes, integrated in signaling cascades mediated by auxins during LR and callus formation, as a particular feature of RKN-FS distinct to CNs. However, LBD16, and its positively co-regulated genes, were repressed in syncytia, suggesting a selective down- regulation of the LBD16 auxin mediated pathways in CNs-FS. Interestingly, cytokinin-induced genes are enriched in syncytia and we encountered similarities between the transcriptome of shoot regeneration from callus, modulated by cytokinins, and that of syncytia. These findings establish differences in the regulatory networks leading to both FS formation, probably modulated by the auxin/cytokinin balance.

Both epiphytic and endophytic strains of Rhodococcus fascians influence transporter gene expression and cytokinins in infected Pisum sativum L. seedlings

Czech Academy of Sciences Publication Activity Database

Dhandapani, P.; Song, J.; Novák, Ondřej; Jameson, P. E.

2018-01-01

Roč. 85, č. 2 (2018), s. 231-242 ISSN 0167-6903 R&D Projects: GA ČR(CZ) GA17-06613S Institutional support: RVO:61389030 Keywords : Amino acid transporter * Cell wall invertase * Cytokinin * Pea * Rhodococcus fascians * Sucrose transporter * Sugar Will Eventually be Exported Transporter (SWEET) Subject RIV: EF - Botanics OBOR OECD: Plant sciences, botany Impact factor: 2.646, year: 2016

Genetics Home Reference: glucose-6-phosphate dehydrogenase deficiency

Science.gov (United States)

... deficiency Encyclopedia: Glucose-6-phosphate dehydrogenase test Encyclopedia: Hemolytic anemia Encyclopedia: Newborn jaundice Health Topic: Anemia Health Topic: G6PD Deficiency Health Topic: Newborn Screening Genetic and Rare Diseases Information Center (1 link) Glucose-6-phosphate dehydrogenase ...

Differentiating inflamed and normal lungs by the apparent reaction rate constants of lactate dehydrogenase probed by hyperpolarized (13)C labeled pyruvate.

Science.gov (United States)

Xu, He N; Kadlececk, Stephen; Shaghaghi, Hoora; Zhao, Huaqing; Profka, Harilla; Pourfathi, Mehrdad; Rizi, Rahim; Li, Lin Z

2016-02-01

Clinically translatable hyperpolarized (HP) (13)C-NMR can probe in vivo enzymatic reactions, e.g., lactate dehydrogenase (LDH)-catalyzed reaction by injecting HP (13)C-pyruvate into the subject, which is converted to (13)C labeled lactate by the enzyme. Parameters such as (13)C-lactate signals and lactate-to-pyruvate signal ratio are commonly used for analyzing the HP (13)C-NMR data. However, the biochemical/biological meaning of these parameters remains either unclear or dependent on experimental settings. It is preferable to quantify the reaction rate constants with a clearer physical meaning. Here we report the extraction of the kinetic parameters of the LDH reaction from HP (13)C-NMR data and investigate if they can be potential predictors of lung inflammation. Male Sprague-Dawley rats (12 controls, 14 treated) were used. One dose of bleomycin (2.5 U/kg) was administered intratracheally to the treatment group. The lungs were removed, perfused, and observed by the HP-NMR technique, where a HyperSense dynamic nuclear polarization system was used to generate the HP (13)C-pyruvate for injecting into the lungs. A 20 mm (1)H/(13)C dual-tuned coil in a 9.4-T Varian vertical bore NMR spectrometer was employed to acquire the (13)C spectral data every 1 s over a time period of 300 s using a non-selective, 15-degree radiofrequency pulse. The apparent rate constants of the LDH reaction and their ratio were quantified by applying ratiometric fitting analysis to the time series data of (13)C labeled pyruvate and lactate. The apparent forward rate constant kp =(3.67±3.31)×10(-4) s(-1), reverse rate constant kl =(4.95±2.90)×10(-2) s(-1), rate constant ratio kp /kl =(7.53±5.75)×10(-3) for the control lungs; kp =(11.71±4.35)×10(-4) s(-1), kl =(9.89±3.89)×10(-2) s(-1), and kp /kl =(12.39±4.18)×10(-3) for the inflamed lungs at the 7(th) day post treatment. Wilcoxon rank-sum test showed that the medians of these kinetic parameters of the 7-day cohort were significantly

Short communication. N-(2-chloro-4-pyridyl)-N-phenylurea (4-CPPU) enhances in vitro direct shoot organogenesis of Citrus aurantium L. epicotyl segments compared to other commonly used cytokinins

Energy Technology Data Exchange (ETDEWEB)

Roussos, P. A.; Dimitriou, G.; Voloudakis, A. E.

2011-07-01

The effect of three concentrations of five different cytokinins, i.e. 6-benzylamino purine, 2-isopentyl adenine, kinetin (Kin), thidiazuron and N-(2-chloro-4-pyridyl)-N-phenylurea (4-CPPU), was evaluated on the in vitro direct shoot organogenesis of epicotyl explants of sour orange (Citrus aurantium L.). The basal medium used was that of Murashige and Tucker and epicotyl explants were incubated in medium supplemented with the prementioned cytokinins for 45 days. The addition of Kin and 4-CPPU in the medium enhanced the direct shoot organogenesis of sour orange epicotyl segments. The concentration of each of these two cytokinins which gave the best results, was combined with indole-3-acetic acid (IAA) or {alpha}-naphthalene acetic acid ({alpha}-NAA) at concentrations ranging from 0.01 mg L{sup -}1 to 0.2 mg L{sup -}1. The inclusion of IAA at 0.2 mg L{sup -}1 in the medium with 4-CPPU at 0.05 mg L{sup -}1 resulted in 100% successful direct shoot organogenesis, while the combination of Kin at 0.25 mg L{sup -}1 with IAA or {alpha}-NAA each at 0.01 mg L{sup -}1 presented equally high organogenesis percentages (91.7%). The incubation of the produced shoots, in medium supplemented with either indole-3-butyric acid or {alpha}-NAA resulted in high rooting percentages (up to 90%) and the rooted explants were successfully acclimatized under mist (85%). Although 4-CPPU has been used in in vitro culture of various species, this is the first report on its use in the direct shoot organogenesis of citrus species and could be of great value in citrus genetic transformation protocols using epicotyl segments, since this cytokinin resulted in the absolute organogenesis percentage. (Author) 20 refs.